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PART I

* Safety

PHYSICAL REQUIREMENTS

Physically a shipyard outside machinist will need to meet no special requirements other than that he have no physical handicaps, since his work calls for use of all his faculties and limbs. He must necessarily be healthy because the work is physically hard. To be a successful mechanic, one should be mechanically inclined and able to analyze the specific job he is called upon to do.

HEALTH

Knowing that the loss of an eye, limb, or health may impair his usefulness in his trade, a mechanic should be careful to acquire correct habits in performing his work. In going up and down ladders and companionways he should face the ladder or companionway. In climbing, he should make certain of good hand holds and sure footings. He should keep his balance at all times while working on scaffolding and make a practice of avoiding awkward positions during all operations performed while on a scaffold. Rope-hung scaffolding should be anchored with tie ropes to prevent swaying.

Hazards

There are a few hazards that, perhaps, are peculiar to the shipyard outside machinists' work and deserve special attention, namely; The danger of fire and explosion from gas and inflammatory material in pipe lines, pumps, etc., and the danger of someone's releasing steam or hot water into an open pump or pipe line around which work is being performed.

EXPLOSIONS AND FIRE

Explosions and fires are most likely to occur aboard tank ships that have carried inflammatory or explosive cargoes previous to work being done upon them. Cargo tanks are "gas freed" before repair work is started on them. The workman should check with the chemist before starting work, for the pipe line may still contain dangerous liquids or gases. The only safe procedure in disconnecting equipment that has contained or may still contain dangerous materials is to disconnect the equipment to be worked upon and take it out into the open. If it is necessary, a hacksaw or chisel may be used to work on equipment, but there is still danger of friction heat or a spark causing a serious accident.

It should be remembered that fuel lines and tanks on any type of ship present the same fire and explosive hazard as lines on tank ships.

Steam and hot water lines may be temporarily freed of steam or hot water by closing a valve between the equipment to be worked on and the source of steam or hot water. The problem is to prevent the valve from being opened until it is safe to open it. Locking the valve, disconnecting and capping the pipe, or blanking out a flange coupling between the work and the valve are safe practices. Be sure to remove the blanks when the job is finished. Signs on a valve are not trustworthy because there are workmen who do not believe in signs.

All manholes, hatches, and other openings normally are covered or closed. When it is necessary to open these covers to get at work through these openings, a helper should stand guard to keep someone from falling into the opening and to prevent someone's replacing the cover and locking anyone inside. While this may not be fatal, at least it is an unpleasant experience.

Shafts and other equipment are lowered into and pulled out of the hold of a ship by means of ropes. These ropes must be tied securely, and they must be in good condition. If there is a connection on the shaft, any good knot will be sufficient to hold; but where there is no connection, two clove hitches should be tied around the shaft to hold it. A clove hitch is not difficult to tie. It is used because it gets tighter as the pull becomes greater, and when the pull is slacked off it is easy to untie. See Fig. 1. Other forms of slings and lifting devices are employed for certain jobs. Such information will be given in connection with the job later on.

Fig. 1

When lifting a crank shaft, precaution should be taken to keep the shaft from turning. If the shaft should turn while lifting, there is danger of serious injury in someone's getting caught between the turning crank and a stationary object.

Before lifting a heavy load with a steel cable, the operator should carefully examine the cable for defects and kinks.

When lifting extra heavy loads, fasten with pads welded to the load instead of shackles and beam clamps. The welded pad will not slip or break as easily as the shackles and clamps.

Keep on guard and in the clear as much as possible when using heavy strong backs and pull bolts with hydraulic jack. If something should break or slip there is danger of personal injury.

Always keep entirely out from under lifted loads. Any load is likely to slip or break loose.

Be extremely careful when opening up cargo pumps and valves in cargo line. There may be gas in line or pump which may cause a fire.

When working on boilers where one boiler has steam on it, be sure that the valves do not leak before opening up. In some cases, blanks have to be used in the boiler feed line, auxiliary steam line, and the blow-down line. Be sure to remove blanks when job is finished.

When working on boilers, one of which has steam on, the man in charge of the job should lock the connecting valve between the boilers with a chain and padlock.

Wear goggles at all times when using grinding wheels or chipping guns, also when using hot bearing metal.

Keep tools in good condition at all times.

In hooking or tying loads always use wire cable sling in preference to a chain.

When eye bolts are used for hooking heavy loads, the bolt should be screwed down full to the eye. If threads will not permit this, use washers or nuts as spacers. Keep cables as nearly vertical as possible.

Never use two hand hammers or sledge hammers against each other. If necessary to use a handle tool, secure backing-out hammer or set hammers to place against the work. When hand hammers or sledge hammers are hit together, a piece is likely to chip off because of their degree of hardness, and cause personal injury. This practice is especially dangerous because it invites eye injury.

Use common sense at all times to avoid injury. Determine the safest method to do a job and do it the safe way even though it may take a little more time.

QUESTIONS AND ASSIGNMENTS

1. What are the physical requirements for an outside machinist?

2. Name some of the hazards of the shipyard outside machinist trade.

3. Under what conditions are explosive gases encountered?

4. What precautions should the workman observe when working where explosive gas may be encountered?

5. What safety measures should be taken when working on steam, gas, hot water, or oil connections?

6. What precautions should be taken while working in manholes or similar openings?

7. Demonstrate the proper method of tying a rope around a shaft.

*Adapted from "Shipyard Outside Machinist" by State Department of Education, Alabama.

Location of Shops

New men should become familiar with the locations of the various store rooms, tool rooms, stock piles, and other places about the shipyard. Instructions are given to new men by the group leader or some person whose responsibility it is to instruct new men as soon as they reach the yard.

Outside machinists and helpers are called upon to get material, tools, and equipment from many parts of the shipyard during the course of a day's work. It is the duty of every man employed on the job to give strict attention to instructions about how to find his way around in order that no time may be lost.

The store rooms are usually located immediately under the ways upon which the ship is being erected. Tool rooms, where various tools and special equipment are kept, are located at certain points in the shipyard where they may be reached in a reasonable length of time. The workman's badge must be shown at all tool rooms and store rooms, and necessary orders for materials must be obtained from group leaders before such tools and supplies will be issued. Keep this in mind and save time and confusion. Workmen who are not sure should ask someone in authority before starting out on an errand.

Be on the alert at all times when crossing the yard or when walking along traffic lanes. Watch for overhead hazards, and avoid making the other fellow try to guess what you are going to do next. Do not change direction quickly without first making sure the way is clear.

Tools and Equipment

A FIRST CLASS OUTSIDE MACHINIST IS EXPECTED TO HAVE THE FOLLOWING TOOLS:

1. 6" Steel Scale
2. 6' Steel Tape
3. Combination Square, 12" Blade with Centerhead and Protractor
4. 10" Lock Joint Inside Caliper - of Different Sizes
5. 8" Lock Joint Outside Caliper
6. 8" Dividers
7. 10" Dividers
8. 8" Hermaphrodites
9. 1 1/4 lb. and 1 3/4 lb. Machinists' Hammer (Ball Peen)
10. 4" Prick Punch, Size D, Starrett Catalog No. 26 or equal
11. 5" Center Punch, Size E, Starrett Catalog No. 26 or equal
12. Hack Saw, 12"
13. Tin Snips, 10" to 14"
14. Open End Wrenches up to 1 inch
15. Screw Driver, 6" to 10"
16. 6" Level
17. Pocket knife
18. Plumb Bob and Line
19. Scriber
20. Thickness Gauge, .002 to 1/16 inch or more
21. Several Adjustable Wrenches, Suggested Sizes: 4", 6", and 10"
22. Stillson Wrench, 14"
23. 10" Monkey Wrench
24, 6" Pliers
25. Set of 12 Point Box Wrenches up to 1" Size

Tools and Equipment

TOOL CRIB: TOOLS FOUND IN TOOL CRIB, USUALLY COMPANY OWNED

1. 50' Steel Tape
2. Files: Assorted
3. Cold Chisels: Flat, Round Nose, Gouge, Cape, Diamond Point
4. Reamers: Hand, Shell, Roughing, Taper
5. Hack Saw, 12"
6. Tin Snips, 10" to 14"
7. Drift Punches, 1/8" to 3/8", Assorted Sizes
8. Caulking Tools: Air
9. Fox Wedges
10. Taps and Dies
11. Chalk Line
12. Hand Scraper
13. Flat and Bull Nose Scraper
14. Straight Scraper
15. Three Corner Scraper
16. Micrometer
17. Straight Packing Hook
18. Screw Packing Hook
19. Approved Set of Goggles
20. Oil Stone
21. Drifts and Drift Punches
22. Stillson Wrench over 14"
23. Drills
24. 12 Point Box Wrench
25. Hexagon Box Wrench
26. Trammels
27. Straight Edge: 2' to 8'
28. Socket Wrenches
29. Thread Gauge

General Arrangement of a Ship

SHIP TERMS AND LOCATIONS

1. Ship's Anchor 2. Anchor Windlass 3. Chain Locker 4. Ammunition Trunk 5. Dry Cargo 6. Ammunition Chamber 7. Fore Peak Tank 8. Deep Tank 9. Pump Room Forward 10. Cofferdam 11. Walk Way or Cat Walk 12. Ship's Cargo Booms 13. Foremast 14. Navigating Bridge and Quarters for Officers 15, Life Boat 16. Fresh Water Tanks and Storage Place 17. King Post 18. Hose Boom (Booms for Lifting Hose to Make Fast--For Loading Cargo) 19. Main Mast 20. No. 1 Cargo Tank 21. No. 2 Cargo Tank 22. No. 3 Cargo Tank 23. No. 4 Cargo Tank 24. No. 5 Cargo Tank 25. No. 6 Cargo Tank 26. No. 7 Cargo Tank 27. No. 8 Cargo Tank

28. No. 9 Cargo Tank 29. Ventilator and King Post 30. Smoke Stack 31. Life Boats 32. Quarters for Officers 33. Quarters 34. Cofferdams at Sides 35. Cargo Pump-Room 36. Cargo Pump-Room Trunk 37. Fuel Oil Tanks 38. Turbo-Generator 39. Main Propulsion Motor 40. Boiler 41. Distilled Water Tank 42. Propeller Shaft 43. Feed Water Tanks or Double Bottom Tanks 44. Feed Water Tanks or Double Bottom Tanks 45. Propeller 46. After Peak Tank 47. Steering Gear 48. Fresh Water Tank 49. Rudder 50. Bosun's Stores 51. Chain Locker 52. Deep Tank and Dry Cargo 53. Forward Pump Room 54. Cargo Tank No. 1 Port 55. Cargo Tank No. 1 Starboard

QUESTIONS

1. Cargo tanks are numbered 1 to 9. Is No. 1 Cargo Tank forward or aft?

2. State the location of the cargo pump room.

3. Where are the fuel oil tanks located?

4. Is the main propulsion motor nearer to the bow or the stern of a tanker?

5. What is the purpose of the propeller shaft?

6. When facing the stern of a ship, is the port side on the right or on the left?

7. Explain the reason for the steering gear and give the location.

8. Where is the deep and dry cargo tank located?

9. Cargo tanks have port wing, center, and starboard wing divisions. Are these divisions separated from each other?

10. What jobs will be done by the outside machinist in the engine room?

11. Give the location of the engine room.

12. What is the name of the deck on which deck stands are installed?

13. Where are the cargo pump valves located?

14. What is meant by the cargo pump room trunk?

Mechanics' Scale

RULES AND SCALES

Several types of scales are used by outside machinists as they go about their work. "Scale" is the term or name given to what a carpenter calls a rule.

STANDARD MEASURE

In order for the outside machinist to have his work agree with the blueprint he must follow the sizes given and measure from the center lines or other points exactly as shown. He must use the same type of measuring tool which was used by the draftsman. It follows, then,

SCALE DIVISIONS

When we examine a scale, we find there are many marks or fine cuts along the edge of the tool. These marks are for the purpose of dividing the length of the scale into many equal parts. No matter how long the scale may be, each inch is found to be exactly the same length. If all the work to be measured was an exact number of whole inches in size, a scale divided into inches would serve the purpose. But this is not so.

READING MEASUREMENTS

Measurements are given in feet and inches, or in feet, inches, and parts of an inch. For example: A certain piece of steel plate or steel strip, may be measured and the length found to be 2 feet, 4-1/2 inches; the width 1 foot, 2 inches; and the thickness 3/4 of one inch. Another way of saying the same thing would be: 2' 4-1/2" x 1' 2" x 3/4". The x used here means "by". For example: 2" x 4" is read "two by four inches". Sizes are sometimes given in feet and inches, and sometimes the sizes are given in inches or parts of one inch.

READING MEASUREMENTS CORRECTLY

A mechanic must be able to read a scale quickly or he is not a good mechanic. He will lose a lot of time and cause others to lose time unless he can read a scale correctly, at the first attempt. The mechanic must thoroughly understand the markings on the scale before he can read it correctly.

ONE INCH GRADUATIONS

Suppose we talk about a one-foot scale first. There are 12 inches in one foot; so a one-foot scale would have 12 equal spaces, but not 12 marks or dividing lines. The lines mark off the spaces. The spaces are called graduations,. With a scale like this we could measure as close as one inch. See Fig. 3.

Fig. 3

HALF-INCH GRADUATIONS

Fig. 4

Now the markings on the scale show two graduations or divisions of the same length in one inch. The scale may be used to measure as close as 1/2 inch. But the work has to be much closer than 1/2 inch. Therefore, the graduations or divisions must be made still finer. Fig. 5 shows about two inches of a mechanic's scale divided into very small parts. Examine Fig. 5 carefully and it is plain that there are 64 spaces between the left-hand end of the scale and the mark numbered "1". Therefore, these graduations are each 1/64 of one inch long.

Fig. 5

The markings on the scale between the mark numbered "1" and the mark numbered "2" divide this inch into 32 parts. Therefore, these graduations are each 1/32 of an inch long. At the same time, it is plain that the longest marks divide the inch into halves, (1/2); the next longest marks divide the inch into quarters, (1/4); and so on down to the finest graduation.

It should be clear that there are:

2 halves in one inch	- Read each division 1/2 inch
4 quarters in one inch	- Read each division 1/4 inch
8 eighths in one inch	- Read each division 1/8 inch
16 sixteenths in one inch	- Read each division 1/16 inch
32 thirty-seconds in one inch	- Read each division 1/32 inch
64 sixty-fourths in one inch	- Read each division 1/64 inch

Notice that each division or graduation is just half of the one before and that the figure used to name the graduation is just twice as large as the one before. The finest measurement that may be taken with a scale divided or graduated as above is 1/64 of an inch.

TYPES OF SCALES

There are several types or kinds of mechanics' scales. One scale widely used is a six-foot tape, made of steel ribbon. The steel ribbon is about 1/4" to 3/4" wide and very thin. The steel ribbon is graduated as fine as 1/16" and rolls up into the casing. Some casings have a spring inside to help in winding up the tape. See Fig. 6.

Fig. 6

USING THE TAPE

A small tab is shown on the end of the tape in Figure 6. This tab may be hooked over the end or edge of a piece of material while the mechanic stretches the tape tightly. The reading is then taken. A tape must never be allowed to "sag" or get slack when measuring the work. Always take the measurement from the inside of the tab.

FIFTY-FOOT STEEL TAPE

Another type of steel tape is 50 feet long. Very long measurements are taken with a fifty-foot steel tape. These tapes must be used correctly or wrong measurements will result. On the end of the tape there is a loop of stiff wire. See Fig. 7.

Fig. 7

CAUTION

Notice that it is one inch from the outside end of the loop to the Figure "1" on the tape. This loop prevents the tape from being lost in the casing when the mechanic winds it up after using. Always measure from the outside end of the loop. Do not allow the loop to become folded over or under.

All steel tapes used where accuracy is required should be checked frequently with the tape belonging to an official of the company and kept by him for this purpose. Some mechanics check their tapes twice a week on regular days, Monday and Thursday, before starting work on those days. To make the check, reel out the official's tape far enough to check the total footage marked on the tape to be used on a specific job. Run out the tape to be checked, place the zero of each tape even, and check the highest foot mark on the tape with that foot mark on the official's tape. If they correspond exactly, the tape checked may be put into use. If there is any discrepancy at the highest foot mark, do not use this tape for accurate work.

In using a steel tape always keep it straight. Never hold it or lay it down in such a way that it will kink. A kinked tape is inaccurate and will soon break.

In placing the one-foot mark on a point, the center of the scale mark must be put exactly on the point. Never walk on a tape or drop anything on it, because it is a fragile, sensitive tool.

When measurements are to be taken that will necessitate unreeling the full length of the tape, unreel the full length and carefully lay the tape alongside the line on the floor where measurements are to be made. Stand the reel or case up on the floor to keep all of the tape right up to the case perfectly flat.

If a tape is to be left any length of time stretched out on the floor, lay template boards close up to the tape for the full length of the stretched-out portion. The edge of the template board will prevent

To pull a steel tape to get slack out of it, place the thumb on top of it and fingers of the same hand under the tape and pull. Do not press the thumb to the floor. To do so will make a sharp bend in the tape back of the thumb and may permanently damage the tape by kinking it. Pull the tape at a point 12 inches beyond a mark, and press the tape to the floor at the mark which will be 12 inches from the thumb and fingers pulling the tape, and no possible kink can result. See Fig. 8.

Fig. 8

FOLDING RULE

Six-foot folding rules, either metal or wood, are often used to advantage. With care, very close measurements may be taken. The rule folds up into 12 sections which makes a small bundle about 7-1/2 inches long, 3 to 3-1/2 inches wide, and possibly 3/4 inches thick, depending on the width of the rule.

Fig. 9

SPECIAL FEATURES

This is a very handy rule for several 'reasons: The rule may be adjusted at the joints to form an angle; the rule may be pushed up as high as a man can reach, straight overhead without buckle; or it may be

ACCURACY OF THE FOLDING RULE

A folding rule is not so accurate as a steel tape, for when the rule becomes worn at the joints, a difference of as much as 3/16 of an inch error is possible in six feet, owing to the looseness of the joints. Therefore, a steel tape is always the better to use when accurate measurements are to be taken. Six-foot rules are graduated to 1/16 of an inch. From this fact it is clear that this type of rule was not. intended for very close measuring.

Fig. 10

THE SIX-INCH STEEL SCALE

Many jobs require the use of a six-inch steel scale. These scales are graduated to 64ths of an inch and are used when measuring for "chock-fitting", checking diameters of holes and shafting, and other fine measuring work. The chock-fitter also uses a six-inch scale as a straight-edge when testing small chocks for a level surface. See Fig. 10. When measuring for chocks, all sizes are given to the shop in 64ths.

Fig. 11 Measuring the depth and width of a slot. The slot is 3/4" wide. Hold the scale square with the surface from which the measurement is taken. Fig. 13

Fig. 12 Lay the scale parallel with the center line of the piece. This cylinder is 4-5/8" long. Notice when the 1" graduation is placed at the end of the piece the dimension reads 1" less than shown at the other end of the scale. Fig. 14

Hold the scale firmly with one hand while marking with the scriber held in the other hand. See Fig. 15. If the scale slips, chalk the surface of the work and begin all over. One line is enough. Two or more lines only confuse the mechanic.

When measuring the diameter of a cylinder, measure exactly across the center of the cylinder to avoid error. See Fig. 16. Where this cannot be done use calipers. See Fig. 23, Calipers, Dividers, etc.

When measuring the diameter of a hole, measure exactly across the center of the hole. Tilt the scale just enough to catch against the side of the hole. Swing the scale back and forth just enough to make sure to measure the full diameter. See Fig. 17.

When measuring the thickness of an irregular piece, hold the scale parallel with the center line of the hole. Use another scale in the left hand as a stop from which to measure. See Fig. 18. A hook rule could be used on this job to good advantage.

QUESTIONS

1. Explain the purpose of the marks on a mechanic's scale.

2. Which is the graduation: The mark? or the space between the marks?

3. Are all sides of a scale graduated in quarter inches?

4. When measuring with a six-foot tape, is the measurement taken from the outside or inside of the tab?

5. When measuring with a 50' tape, is the measurement taken from the outside or inside of the wire loop?

6. What are the finest graduations on a six-inch scale?

7. Name one or two places where the six-inch scale may be used as a straight edge.

8. Explain the advantages and disadvantages of a folding rule.

9. What precautions should be taken when measuring with a fifty-foot steel tape?

10. Is it better to measure from the end of a scale or from a graduation mark when taking a close measurement? Why?

ALL CENTER LINES ARE IN THE CENTERS OF OPENINGS

2. How long is opening "G"?

3. What is the total width of opening "G"?

4. What is distance "Y"?

5. Give the distance from C.L. "A-A" to C.L. "H-H".

6. What is the vertical distance from center of opening "A" to center of opening "D"?

7. State the horizontal distance from C.L. "K-K" to C.L. "H-H".

8. What is the distance from C.L. "B-B" to C.L. "C-C"?

9. How much does distance "Z" measure?

10. Measure distance from C.L. "C-C" to center of opening "A".

Calipers, Dividers, and Morphs

PURPOSE OF CALIPERS

Diameters of shafting, sleeves, holes in couplings; the thickness of plates; sizes of rods and distances between faces, have to be measured very accurately. These items just mentioned have to fit other parts when installations are made throughout the ship.

USING CALIPERS AND A SCALE

It is impossible to measure these sizes accurately by using only a scale. The machinist uses a tool called a caliper to obtain the size or distance and then places the caliper on the scale to read the measurement. Illustrations of the use of calipers are shown on succeeding pages.

CARE OF CALIPERS

Calipers should not be allowed to get rusty. A little oil or wiping with an oily rag will prevent rust. Never use a caliper roughly. Allowing calipers to be thrown around or to become mixed up with bolts and other material on the job will destroy their accuracy.

KIND OF CALIPERS

There are two kinds of calipers: Outside calipers and inside calipers. See Figs. 19 and 20.

SPECIFIC USE OF INSIDE CALIPERS

Inside calipers are used to measure inside diameters of holes or the distance between two faces or surfaces. See Figs. 21 and 22. It is important to keep the caliper at right angles with the work.

SPECIFIC USE OF OUTSIDE CALIPERS

Outside calipers are used to measure the diameters of shafting, cylinders, the thickness of plates, the diameters of bolts, and the distances from outside to outside of two surfaces. See Figs. 19, 23, and 24.

CONSTRUCTION OF CALIPERS

Calipers are made with a "firm joint" or with a "C" spring joint. See Figs. 19 and 25.

CHECKING OUTSIDE DIAMETERS CORRECTLY

Measuring the outside diameter of a shaft or a bolt is a common use for outside calipers. The procedure is as follows: Hold the work, or piece to be measured, in the left hand and adjust the calipers with the right hand until the caliper points will just pass over the work with a slight "feel". The instructor will demonstrate how this feel is obtained. When the work is too heavy to hold in the hand, make sure the caliper passes a short distance beyond the center of the work. For accurate results, the caliper must be held at right angles or square with the center line of the piece being measured. See Figs. 19 and 23.

The process of adjusting the calipers to the work is called "setting the calipers"; and after the adjustment has been completed, the caliper is said to be "set". Never pick up a pair of calipers and change the "set" without first finding out if it is all right to do so. Someone else may be using that setting for some important measuring which was hard to get.

CHECKING INSIDE DIAMETER WITH OUTSIDE DIAMETER

Sometimes it becomes necessary to find out if a certain shaft will fit a hole in a piece of work. If the job is small enough to carry around easily, it is a simple matter to pick the shaft up and try it in the hole. Many pieces, however, are too heavy to do this; it is then necessary to measure the hole, or the shaft, with the right caliper and then set the other caliper to the first caliper used. See Fig. 26.

POCKET SLIDE CALIPER

A very convenient form of caliper is the pocket slide caliper. See Fig. 27.

These slide calipers come in two sizes, 3-inch and 5-inch. The three-inch size has a capacity for measuring inside or outside diameters up to 2 inches. The five-inch size has a capacity for measuring inside or outside diameters up to 3 1/2 inches. There are two register marks on the sliding part of the caliper. One mark is used when measuring inside diameters, and the other mark is used when measuring outside diameters. A convenient lock nut may be tightened to hold the setting. The approximate diameter of the work may be read without removing the slide caliper.

HERMAPHRODITE CALIPERS

Hermaphrodite calipers, commonly called "Morphs", are used principally for scribing lines parallel with surfaces or edges. The points are hardened and may be adjusted up or down for the best results. See Fig. 28.

DIVIDERS

Dividers are made in many sizes and in many styles. The Yankee pattern divider, shown in Fig. 29, is most commonly used. The points are hardened and great care must be taken not to break these important parts of the divider. Close work cannot be done with a stubby divider point.

Dividers are used to make circles, find centers of circles, find centers of broken bolts, divide distances into equal spaces, and other such operations. Lay the dividers down as flat as possible when setting them to scale dimensions. This saves the points, and greater accuracy is possible. See Fig. 30.

QUESTIONS

1. Why is a caliper used to measure instead of measuring with a scale?

3. State the purpose of an hermaphrodite caliper. (Morphs.)

4. What may be the result if the "setting" of calipers or dividers is changed before finding out if someone is using the tool?

5. Which tool is used to make a circle?

6. Explain why it is necessary to keep divider points sharp.

7. Which tool is used to scribe a line parallel to an edge or surface?

8. In measuring the diameter of a hole which caliper is used?

Fig. 19 - Lock-joint Outside Calipers

Measuring the thickness of a piece of steel plate. When the calipers are set, find the scale reading as shown by Fig. 24.     Measuring the distance between two faces.

Fig. 20 - Lock-Joint Inside Calipers

Using inside calipers to measure the distance between tow plates such as a machine base and a foundation. The distance is found by trying the calipers on a scale after measuring. The instructor will demonstrate the correct way to place the calipers on the scale.

Fig. 21

Fig. 22

Fig. 23

Pass the calipers back and forth over the shaft until the points just touch. Keep the calipers square with the center line. The instructor will demonstrate this.

Fig. 24

One point of the calipers should always be held against the end of the scale as shown. Never try to check a size by having both points on the scale.

These calipers are adjusted with a screw and thumb nut. Inside calipers are made of the same type. The "C" spring keeps the caliper at the "open" position.

Fig. 25

Fig. 27 - Pocket Slide Caliper
 

Fig. 28-Lock-Joint
Hermaphrodite

Scribing a line parallel with the edge of the work.

Fig. 29 - Typical "Yankee" Pattern, String Dividers

Hardened points, screw adjustment. Dividers with dull or broken points are useless.

Fig. 30

Fig. 30 shows dividers set to 1-1/4" on the scale. Always lay the dividers down flat, with the points in a graduation mark. Doing this will protect the points from being dulled, and a closer setting may be obtained because a clear view may be had of the scale and divider points.

PURPOSE OF MICROMETERS

The ordinary type of mechanics' scale is graduated as fine as 64ths of an inch only. Many measurements must be taken which are much finer than this. Such measurements are so fine that it would be impossible to engrave the dimensions on a scale so they could be read. The tool which is used to do this fine measuring is called a micrometer, and it is possible to measure sizes to .0001 of an inch. Fig. 31 illustrates the general construction of an outside micrometer and gives the names of the principal parts.

OUTSIDE MICROMETERS are used to measure outside diameters and thicknesses. INSIDE MICROMETERS are used to measure inside diameters, the distance between surfaces, and other similar dimensions.

CAPACITY OF MICROMETERS

Micrometers are listed according to the measuring capacity. See Starretts catalog No. 26, pages 97-139, for complete details.

Fig. 31

Diameters of shafting, drills, reamers, machined and ground pins and thicknesses of accurately machined plates or bars, may be measured with micrometers.

When speaking of a one-inch micrometer it is understood that any measurement from nothing up to and including 1 inch may be taken. 4 two-inch micrometer measures distances from 1 inch up to and including 2 inches; a three-inch micrometer is used for jobs from 2 inches up to and including 3 inches, and so on.

Fig. 32 - Inside Micrometer

Inside micrometers, see Fig. 32, are equipped with extension pieces called rods and a handle for getting the tool into narrow places. The instructor will demonstrate the use and handling of micrometers.

The figures on the thimble (Fig. 31) show that the thimble is graduated all around. These graduations are exactly twenty-five in number. Moving the thimble one graduation, opens or closes the gap between the anvil and spindle nose .001 of an inch (one thousandth).

The setting on the illustration, Fig. 31, is .151 of an inch. On Fig. 32 the setting is .175 of an inch. Reading micrometers is simply a matter of counting the number of full turns of the thimble on the sleeve and adding the number of spaces on the thimble which have passed the zero mark.

For example: Measuring 1/8 inch with a scale is the same as .125 when measuring with micrometers, except that the micrometer measurement is much closer.

The decimal equivalent table, Page 33, illustrates how easy it is to select the correct decimal for any fraction found on a mechanic's scale.

ADDING AND SUBTRACTING

When adding 3-1/2, 2-1/4, 4-11/16, 9-5/16, 2-3/16, 1-9/64, it is much easier, quicker, and more accurate if done this way:

3.5 2.25 4.6875 9.3125 2.1875 1.140625 -------- 23.078125 or 23-5/64

Always be sure to have the decimal points directly in a vertical line, and check the addition from top to bottom after adding.

The value of .078125 is found in the table of decimal equivalents. The total distance may now be laid off with a common mechanic's scale. After a little practice the mechanic will have memorized many of the decimals and will not need to refer too frequently to the table. In any event the decimal equivalent of the fraction can be found by dividing the number above the line by the number below the line.

MULTIPLICATION

When it becomes necessary to multiply 9-11/64 by 15-15/16, the calculation is much easier if decimals are used. For example:

(a) 9.171875 x 15.9375 There are as many decimal position of the places in the product of the two numbers as the total number of places in both numbers.	Place one number under the other, disregarding the decimal points.       9.171875        15.9375        -------       45859375      64203125     27515625    82546875   45859375   9171875 -------------- 146.1767578125
(b) Multiply .037 by .006	.037    .006 ------- .000222

There were only three figures in the answer until three zeros were placed in front of the three twos. This is always done when there are not sufficient figures in the answer to make up the total number of decimal places in the two numbers being multiplied. Always place the zeros before the number. The above result is read: Two hundred twenty two millionths. An easy way to read a decimal is to write the decimal as follows:

extend the decimal point below the line making it into a figure 1 as follows:

then add as many zeros after the one as there are figures to the right of the decimal point above the line as follows:

DIVISION

The division of decimals is sometimes more difficult than addition. subtraction, or multiplication. The placing of the decimal point in the answer is very important. A few examples of placing the decimal point correctly are given below.

Example A:

Divide 2.50 by 1.25 . Move the decimal point to the right, two places, making both numbers whole numbers. Then 125., "goes into" 250., twice.

Example B:

Divide 1.25 by 2.50 . Move the decimal points to the right, two places, making both numbers whole numbers. Then 250 will not "go into" 125. Add a cipher making 125. read 125.0 . Now 200. will "go

Rules for Placing the Decimal Point

The examples given above show that the following rules must be observed:

Rule 1. Move the decimal point to the right in both divisor and dividend the same number of places, in order to change the decimals to whole numbers. Add zeros to the right, in the dividend, to balance the first result by multiplication.

USING RULE 1

Divisor	Dividend	Quotient
1.25)	2.50	(-------

(a) Move decimal point to the right, the same number of places in the divisor and in the dividend.

125.)	250.	(2._____
	25.0

Since there are no decimal places in the divisor or dividend, there are none in the quotient.

(b)

1.25)

.25

(______

Move decimal points to the right, the same number of places in the divisor and in the dividend. A zero is added to the right, in the dividend, to balance the result by multiplication.

125.)	25.0	(.2
	25.0

Rule II. Point off the same number of decimal places in the quotient as the places in the dividend exceed the places in the divisor.

USING RULE II

The decimal point in the quotient in example "b" is placed by Using Rule II. Since there were no decimal places in the divisor and there was one place in the dividend, the places in the dividend exceed the places in the divisor by one. Therefore point off one place in the quotient. The result is .2 .

Rule III. When there are more decimal places in the divisor than in the dividend, add zeros after the last figure in the dividend until the decimal places in the dividend equal those in the divisor. Then proceed as in ordinary division.

NOTE: Add more zeros to the dividend if necessary. Adding zeros to the last figure in the decimal, to the right of the decimal point, in no way alters the value of the decimal. To check the result after dividing a number having decimals by a number which has more decimal places than the number being divided, inspect all of the numbers carefully. The answer should be pointed off to show the number in the

USING RULE III

When the divisor contains all decimals:

.25

250.

(_______

Move decimal points to the right, the same number of places in divisor and dividend.

.25)	25000.	(_______
	25

It was necessary to add two zeros to 250. before the decimal point could be moved two places to the right. When this was done, the problem then was to divide 25000. by 25.

PROBLEMS

Use a separate sheet of paper. Find the answers to the following problems:

Multiply:	1.	3-7/16 by .1875	3.	17.0032 by .0625
	2.	9.25 by 1.375	4.	.0073 by 1/4

Divide:	5.	.375 by .1875	7.	3.1416 by .7854
	6.	1.9375 by .875	8.	2-1/2 by 1.414

CIRCUMFERENCE

The distance around the circumference is Pi times the diameter. What is the diameter of a circle, the circumference of which is 6.28327

DIAGONAL

The distance across the corners of a square is 1.414 times the length of one side of a square.

Find the length of one side of a square when the distance across the corners is 4.2426.

Decimal Equivalents of a Fraction of an Inch

1/64 .015625 1/32 .03125 3/64 .046875 1/16 .0625 5/64 .078125 3/32 .09375 7/64 .109375 1/8 .1250 9/64 .140625 5/32 .15625 11/64 .171875 3/16 .1875 13/64 .203125 7/32 .21875 15/64 .234375 1/4 .2500 17/64 .265625 9/32 .28125 19/64 .296875 5/18 .3125 21/64 .328125	11/32 .34375 23/64 .359375 3/8 .3750 25/64 .390625 13/32 .40625 27/64 .421875 7/16 .4375 29/64 .453125 15/32 .46875 31/64 .484375 1/2 .5000 33/64 .515625 17/32 .53125 35/64 .546875 9/16 .5625 37/64 .578125 19/32 .59375 39/64 .609375 5/8 .6250 41/64 .640625 21/32 .65625	43/64 .671875 11/16 .6875 45/64 .703125 23/32 .71875 47/64 .734375 3/4 .7500 49/64 .765625 25/32 .78125 51/64 .796875 13/16 .8125 53/64 .828125 27/32 .84375 55/64 .859375 7/8 .8750 57/64 .890625 29/32 .90625 59/64 .921875 15/16 .9375 61/64 .953125 31/32 .96875 63/64 .984375
1 1.0000

Machinists' Hammer and Center Punch

PURPOSE OF A MACHINISTS' HAMMER

A machinist uses his hammer for tapping bolts home; for making center punch marks; for chipping with a cold chisel; for driving wedges; for knocking off small pads; for driving pins in and out; for marking gaskets; for cutting holes in gaskets; and for many other such purposes. The principal reason for listing the above operations is to fix in the mind of the student the fact that a hammer has a definite place on the job. The use of a bolt, a bar of steel, or other makeshift, should never be considered. Always use a hammer to do these jobs.

CORRECT USE OF A HAMMER

A careful study of a hammer will show that the handle is evenly balanced in the head. The length of the handle may vary, to suit the individual, but the hand should always grasp the handle close to the outer end and not up at the head end. Holding a hammer close to the head is called "choking the hammer". This is bad practice and causes accidents.

SAFETY

Never strike a hardened surface with a hammer. The face and peen of the hammer are hardened, and two hardened surfaces striking together with force may cause the hammer to "spall"; that is, small chips crack off and fly, which may result in eye injury or cuts.

Never use a hammer with a loose handle or a loose "wedge". The wedge is in the end of the handle to hold it tightly in the head.

Never use the handle as a lever with which to lift or pry.

AN EXAMPLE OF USING A HAMMER

As a hammer and center punch are used frequently, this operation is chosen to describe briefly the correct procedure.

1. When using a prick punch, strike a light blow or use a light hammer. A heavy blow will break the point of the prick punch and may cause the mark to be "off center". See Fig. 34. 2. When using a center punch, see Fig. 35, one should use a heavier hammer. One blow with the right weight hammer is all that is necessary, in most cases. Using a light hammer on a heavy center punch is not permissible. 3. Hold the center punch square with the work unless it is necessary to "draw" the punch mark. See Fig. 36. 4. When using a heavy center punch, strike a light blow first to be sure the mark is "on center". Then set the mark deeper with a heavy blow.

Center punch sizes are given by letter in tool catalogs. However, many mechanics dress their own center punches to suit their own requirements.

CAUTION

The top of the center punch will "mushroom" after repeated use. Grind the mushroom off before it spalls and causes injury. See Fig. 37 for an illustration of good practice.

Fig. 34

Common type of center punch. It has a hardened point. The kurled body gives a better gripping surface for the fingers.

The prick punch. It is smaller and shorter than a center punch. In striking the punch with a hammer, keep the punch straight up and down. when the center mark is not exactly true, lean the punch and "draw" the center over as shown. (Fig. 36.)

Fig. 37

Half size heavy center punch. It is used for very heavy work. Hexagon Steel.

QUESTIONS

1. Why should a hammer always be used instead of some make-shift?

2. State the correct way to hold a hammer and give reasons.

3. Explain why a hardened surface should never be struck with a machinists' hammer.

4. Point out correct practice in using a hammer with a prick punch and with a heavy center punch.

5. What is likely to happen to a prick punch if it is struck too heavy a blow?

6. Explain the different uses of a prick punch and a center punch.

Cold Chisels: Types and Uses

TYPES OF COLD CHISELS

Many different operations have to be done with cold chisels. There are several types of commonly used chisels. See figures below.

The flat chisel, Fig. 38, is used for chipping rough spots off of flat surfaces, chipping off burrs, smoothing edges, and cutting sheet metal. The cape chisel, Fig. 39, is forged narrow one way, but it is wide the other way for extra strength. Narrow grooves, slots, and keyways are cut with the cape chisel.

The diamond point chisel, Fig. 40, is adapted for cutting V-shaped grooves and for chipping out rough spots in square corners.

The gouge chisel, Fig. 41, and the round nose chisel, Fig. 42, are much alike. The gouge is used for roughing out round corners, cutting oil grooves, or drawing a drill to center.

The round nose chisel may be used for trimming round corners off of sheet metal or for roughing off convex surfaces and round corners. Cold chisels may be any width or length to suit the job.

All steel is not suitable for making cold chisels. As a chisel must withstand heavy blows repeatedly, it is not practical to harden the whole tool. After the chisel is forged into the desired shape it is annealed, and the cutting edge is tempered and ground to the desired angle. The temper extends about 3/4 inch from the edge. Flat cold chisels and cape chisels are ground on one face only. The stock used is generally octagon in shape, but round stock is often used.

SAFETY

Mushrooming of the top of the chisel will result from ordinary use. Keep the mushroom down to a minimum by grinding before it spalls off and hurts someone. See Fig. 38 for the correct shape of the head.

Be careful to chip away from anyone working near, and if necessary, give a warning to avoid injuries. Watch for the corner of a chisel to break and fly. Use goggles when chipping.

Figure 43 shows how several cuts are taken off the edge of the piece of metal when chipping. The chip curls ahead of the cutting edge. Taking several cuts is much more quickly and easily accomplished than try to do the job with one cut.

Fig. 43

QUESTIONS

1. Explain why a cold chisel is not tempered for the entire length.

2. What is the principal difference between a flat cold chisel and a cape chisel.

3. What should be done to avoid injury from a mushroomed chisel?

4. What chisel should be used when cutting a narrow groove?

5. Name one necessary safety precaution when chipping.

Open End Wrenches

PURPOSE OF OPEN END WRENCHES

The name "open end" means that the wrench opening, which fits the nut is cut out at the end of the wrench so the wrench may he slipped on the nut from the side instead of setting the wrench down over the nut as is the case with a box type or socket wrench. See Fig. 44.

The wrench may be applied and the nut turned down very rapidly with an open end wrench, but care must be taken to use a wrench of the correct size. The size of the opening is usually stamped on the wrench. Open end wrenches are usually double ended, having different size openings on each end; and the wrenches come in sets.

DETERMINING CORRECT SIZE OPENING In Merchant Marine Work when figuring the size of the opening for a snug fit on the nut, the rule is: Diameter of bolt x 1 1/2 + 1/8". For example: Diameter of bolt 1/2". Size of opening in wrench 1/2 x 1 1/2 + 1/8" = 7/8". The U. S. Navy Standard size of wrench opening is diameter of bolt x 1 1/2.

Fig. 44

For example: Diameter of bolt is 1/2". Size of opening in wrench 1/2 x 1 1/2 = 3/4 in.

When too large a wrench is used, the corners of the nut are chewed off, making it difficult to get the nut on or off. Wrench opening sizes are always measured across the flat of a nut.

CARE OF WRENCHES

Open end wrenches are designed to withstand a pull on the handle about equal to the same force that the bolt will withstand. Hitting the wrench handle with a hammer is poor practice. A jolt with the palm of the hand should be sufficient to tighten the nut, ordinarily. In special cases a short piece of pipe may be slipped over the wrench to give additional leverage. Be very careful in doing this not to break the wrench, or sheer the bolt.

Never use a wrench as a hammer. A battered wrench always gives trouble.

Questions

1. What is the advantage of an open end wrench? 2. Explain why the correct size opening for the nut should always be used. 3. Where is a nut measured to get the size of the wrench opening? 4. State the rule for finding the size of the wrench opening from the bolt diameter. Commercial? U. S. Navy? 5. Explain how a wrench should be used to draw a nut down snugly. 6. Name some of the troubles encountered with a wrench that has been battered by using the wrench for a hammer. 7. How may the troubles, named in question 6, be avoided?

Drills and Drilling

USE OF TWIST DRILLS

The outside machinist drills many holes through steel shafting, deck plates, bulkheads, etc. Twist drills are kept in the tool crib for the purpose of filling the mechanics' needs. As these tools are made of high carbon or high speed steel, they may be easily broken. Either the cutting edges may be chipped or the drill may be snapped off short if the workman does not take care to hold the drill steady while drilling.

DRILL FEEDS

The action of forcing the drill into the work is called the "feed". Too much force applied to the feed, especially with the smaller size drills, will very likely break the drill.

When drilling at an angle, feed very slowly until the drill is cutting "to size". This means until the drill has entered far enough for all of the drill point to be below the surface of the work and then the drill cannot slip, but it can be leaned sidewise and cramped, causing it to break. Be careful to avoid this.

TYPES OF DRILLS

Up to 3/16" in diameter the drill shank is straight. See Fig. 45. A few drills above 3/16" may be straight, but they are usually tapered. Tapered shank drills hold better in the drill chuck without slipping than do straight shank drills. See Fig. 46.

Taper shanks are not all the same size. Larger drills have larger shanks, and of course provision must be made for the drills to fit the drill chuck. All tapered shank drills are usable in one drill chuck by employing taper sleeves in the chuck. The sleeve has a tapered hole which fits the drill shank taper and the outside of the sleeve fits the hole in the drill chuck. Both sleeve and drill must be securely inserted to prevent slipping. See Fig. 49.

FLAT SIDE TAPERS

Most shipyard air drilling machines have a flat side in the chuck taper. There is a corresponding flat-on the taper shank of the drill.

CAUTION

Wipe the hole in the chuck and the shank of the drill With a rag or some clean waste before inserting the drill in the chuck. Never allow dirt or grit to remain on these surfaces. The drill will be thrown out of line and the tapers scored.

When removing the drill from the chuck, use a drift made for the purpose. Never strike the drill to loosen it from the chuck or sleeve.

A drift is a piece of steel tapered like a wedge. The drift thickness fits the width of the slot in the chuck spindle or tapered sleeve. The thin edge of the wedge is inserted in the slot between the end of the drill shank and the upper end of the slot. As the drift (wedge) is driven inward, it forces the drill downward. A light blow is sufficient in most cases.

GRINDING DRILLS

Always examine drills when getting them out of the tool crib. A dull drill never cuts well and is likely to "burn" (lose its temper) if used. If the drill is dull, have it ground or exchange it for another at once. If by some accident or mishandling the drill is broken or chipped while in use, have it replaced or ground immediately. Do not risk spoiling a job by trying to use a faulty tool. Be sure the tool crib attendant furnishes the size drills requested when applying at the tool crib window for drills.

LUBRICATION

When drilling cast iron no lubricant is necessary. Use a light lubricant for steel. The lubricant acts as a coolant and prevents the drill from burning. Sometimes a hard spot is encountered in the metal. Continuous drilling on such a hard spot may ruin the drill point. The addition of lubricant will not help the situation in most cases. Use a high speed drill (this does not mean run the drill at high speed) or chip the hard particle out with a gouge or diamond point chisel. If it is found that the metal is hard, stop at once. Hardened metal must be annealed before it can be drilled. An application of heat with an acetylene torch may help, but the metal should be covered and allowed to cool slowly before proceeding. In case heat is not available or a part can not be heated owing to the grade of steel or other parts near by being affected by the heat, use a little turpentine and grind the drill often.

When drilling brass use a very light oil, or drilling compound. The cutting lips of the drill must be ground with a neutral rake to prevent "hogging in". Hogging is very likely to occur when following a pilot hole. Be sure the cutting lips of the drill are ground to the same length.

STARTING A LARGE DRILL

Drills of 1 1/4" and larger do not start very easily in a center punch mark. The best thing to do in this case is to drill a "pilot hole" first. The size of the pilot hole used is from 3/16" to 1/4". The

There is one thing to watch when drilling the large hole through the pilot hole. The large drill will "hog in" (catch and break) if the feed is not eased up at the finish of the drilling. Go carefully on the first few holes and experience will show just how much to ease up the pressure towards the end of the drilling.

LOCATING A HOLE

All the important holes should be "laid out" before commencing to drill. This is done by prick punching the exact center at the intersection of two lines. The dividers are then used (See Fig. 35) to lay out the size of the hole. Chalk the surface before marking the circle. Prick punch the circle in at least four places. (Large holes need more prick punch marks.) Prick punch marks should be placed about every 1/2" on the circle circumference. Sometimes a "witness" circle is scribed around the hole circle about 1/16" away from the first circle. If the drill begins to "run" it will be noticed at once.

"DRAWING" A DRILL

When drilling a hole without using a pilot hole, the drill may "run off". See Fig. 47. The operator should raise the drill from the work to inspect the cutting location before the drill has gone in far enough to cut to size. If the hole shows signs of running off, chip a groove with a gouge chisel on the wide side or the layout. See Fig. 41. This groove will cause the drill to "bite in" each time the cutting edge hits the groove. If the drill is still off' after a few more turns, chip the groove again until the drill is cutting central with the layout. The instructor will demonstrate the correct procedure.

When drilling a hole following a pilot hole the drill cannot be drawn over. This means that extra care must be used when drilling the pilot hole.

DRILL SIZES

Ordinarily, drill sizes are stamped on the shank in fractions of an inch. Nearly all drills used by the outside machinist are stamped in exact 64ths. For example: 1/4"; 21/32"; 41/64"; 1-17/64"; 1-1/8"; 1-3/16", and many others.

There may be a few cases where it is necessary to use a drill which is not exact 64ths in size. Then "letter" drill sizes are used. Such drill sizes are:

D - .246 diameter, a driving fit for 1/4" diameter pin. N - .302 diameter, a driving fit for 5/16" diameter pin. U - .368 diameter, a driving fit for 3/8"diameter pin.

There is a drill size for every letter in the alphabet. Some Letter sizes are "even" fractional dimensions, such as:

H drill exactly 17/64" diameter .266 M drill exactly 19/64" diameter .295 T drill exactly 23/64" diameter .358

There are many others. (See page 263, Starrett Catalog, No. 26.) For special cases where these drills are to be used, see the instructor.

Circumstances control the cutting speed of drills in most cases. Small drills run much faster than the larger drills. This is a matter for good judgment. A good rule to follow is:

35' per minute for cast iron 60' per minute for steel 60' per minute for brass

If it is found that the drill will cut well, hold its edge, and do a good job at a higher rate of speed; step up the speed.

It is better to run a drill slowly and step up the speed rather than to begin at high speed and possibly burn the drill. Check with the instructor or leader.

DRILLING A FLAT BOTTOM HOLE

Drill the hole to the correct depth, measuring from the center of the drilled hole to the surface of the work. Be careful to measure to the center of the hole. Flat bottom holes are usually drilled in the shop. The outside machinist drills this kind of hole only when instructed to do so. Ordinarily a hole is drilled a little deeper than usual to allow a plug tap to reach the bottom and cut enough thread.

Replace the regular drill with a stub drill: One that has been ground off square on the end. Finish the bottom of the hole flat with the stub drill. Feed slowly and carefully. Sometimes a reamer, cut like an end mill, is used for this job. Check with the leader when there is a job of this kind to do.

Flat bottom holes are tapped when a cap screw or bolt is used. In this case no nut is used on the bolt. The threads are in the hole and the cap screw is turned in with a wrench. Flat bottom holes are also used for studs (bolts with a thread on both ends and a nut on one end.) Removing Studs or Broken Bolts, page 67, Fig. 81.

ENLARGING HOLES ALREADY DRILLED

Consider a 1" hole drilled through a hub or a thick plate. Perhaps it is necessary to enlarge the hole 1/4". The drill will have a tendency to "hog in" when starting the larger drill in the hole. Run the drill slowly and feed lightly. The drill will hog into steel or brass more than it will in cast iron. It may be necessary to grind the "rake" off of the cutting lips of the drill. Check with the leader in such cases.

DRILLING COMPARED WITH BORING

Holes larger than two inches are spoken of in the shop as being "bored". The reason is that the job is done in a boring mill or lathe. When such a job has to be done in the yard, it is sometimes necessary to use a drilling post, or "old man", as it is called. This is a device which may be clamped to the deck or bulkhead, and constant pressure (feed) is applied by means of a screw.

A "drill stick" is also used; it will be explained in the manual later.

For very large holes the boring is done with the use of a "boring bar" and a reduction-driven drill or reamer. This operation will be explained later in another section of the manual.

Fig. 50, Showing a taper shank drill with the shank larger than the drill. Care must be taken not to apply too much pressure and snap the drill at the neck.
Fig. 51 and 52, Two views of a taper shank twist drill with a flat to prevent turning in the chuck.

Top View Of Chuck, Drill, And Sleeve The taper sleeve is used to make up for the difference between the size of the hole in the chuck and the taper shank of a small drill.

Top views of taper shank drill

1. What is understood by a "drill feed"?

2. Explain the difference between a straight shank and a taper shank.

3. Why are the taper shank drills flatted off on one side?

4. What is the correct method of removing a drill from the chuck or sleeve?

5. Explain what is meant by "burning" a drill. What causes it?

6. When is a lubricant on a drill necessary?

7. Explain the action of a lubricant.

8. What is meant by a "pilot hole"?

9. Explain the necessity for a pilot hole.

10. State precautions necessary when following a pilot hole.

11. What is understood by the statement: The drill may "run off"?

12. How is a drill "drawn" back to center?

13. Name two ways to check the size of a drill.

14. What are letter size drills?

15. Is the cutting speed for brass different from that for cast iron? How much different?

16. State two ways to drill a flat bottom hole.

17. Explain the difference between "drilling" and "boring".

18. What is the correct procedure when a drill cutting lip breaks off? State the probable cause.

19. What is a "drift" when mentioned in connection with drilling?

Reamers and Reaming

PURPOSE OF REAMERS

A drilled hole is never so true to size as a reamed hole. Holes are drilled before they are reamed. The reason for reaming a hole is to make a snug, uniform fit for a straight pin, a shaft, a taper pin, a fitted bolt, and other similar fits.

TYPES OF REAMERS

Some reamers are used in an air drilling machine. Reamers are generally classified as:

1. Fluted reamer, taper shank 2. Rose reamer, straight or taper shank 3. Shell reamer, used with a shell-reamer arbor 4. Hand reamers: 1. With spiral teeth 2. With regular (straight) teeth 5. Expansion reamer, hand 6. Taper reamer, hand 7. Taper reamers, machine

SHELL REAMERS are usually large in diameter, running as much as 8 inches. These reamers are hollow. The inside hole is tapered to fit the taper of a specially made arbor, the opposite end of which fits the taper in a drilling machine chuck. Two square driving blocks fit corresponding notches in the shell reamer. Many different sizes of reamers will fit the same arbor. See Fig. 53.

Shell reamers are made either fluted or rose type, and the cutting action is exactly the same as for the smaller sizes.

Fig. 53

THE FLUTED REAMER is used where great accuracy is not required. The teeth are spaced fairly close together and the reamer cuts fast enough for an ordinary job. The cutting is done along the sides of the teeth, which are separated by the flutes. See Fig. 54.

Fig. 54

THE ROSE REAMER cuts only on the end. The teeth are shaped to cut ahead of the body of the reamer. The flutes allow the chips to get out of the hole and also provide a way for the lubricant to get into the cutting end. The rose reamer is not expected to cut a very smooth hole, and it is made a few thousandths under-size, so that the hole may be finished out accurately with a hand reamer. Rose reamers are sometimes used to make a flat bottom hole for a stud. See Fig. 55.

Fig. 55

Fig. 56

THE HAND EXPANSION REAMER is made especially for close work. The reamer has slits along the body and a tapered hole through the center. A taper plug is closely fitted to the taper hole in the reamer, and by means of a screw the reamer teeth can be swelled out to a barrel-like curve, causing the reamer to cut a few thousandths over size. The reason for the expansion feature of the reamer is to provide for its longer usefulness. Any wear is taken up by the taper adjustment. See Fig. 57.

Fig. 57

TAPER REAMERS are made for hand and machine use. When hanging brass operating-rod ends on a deck-stand, the upper and lower collars are secured in the correct location on the rod with taper pins. A taper reamer is used to ream the hole to the correct size. See Fig. 58.

When two holes do not line up exactly in steel plates that are being riveted or temporarily bolted together, a machine taper reamer may be used to cut the opposite edges of the two holes enough to slip a bolt or rivet through.

Fig. 58

Throwing reamers around carelessly, using a reamer for a hammer, leaving a reamer in the drill chuck after using, or anything else that will allow the reamer teeth to become damaged or broken, is not good practice.

Reamers are high-grade tools, very expensive, and sometimes hard to replace. A reamer may be sharpened by grinding in the tool room, but the nicks and broken places cannot be repaired.

Do not allow reamers to get rusty, and do not return them to the tool room dirty.

Be careful to use the correct size holder on a hand-reamer square. If a wrench is used, be sure it fits the square tightly.

Accidents happen with tools. Report broken or damaged tools immediately. This will give the leader a chance to do something about replacements. Do not let the job be held up for lack of planning.

QUESTIONS

1. Name two reasons for reaming a hole. 2. What is the principal difference between hand and machine reamers? 3. Explain the advantage of a spiral reamer as compared with a regular reamer. 4. Why are expansion reamers constructed so that the diameters may be adjusted? 5. Where is the cutting edge on a rose reamer? 6. What is meant by a shell-reamer arbor? 7. Name the type of reamer used to ream a hole for a taper pin. 8. State what type of reamer to use and what to do when two holes are out of line so that a rivet or bolt will not go through. 9. How may the teeth of reamers be ruined? 10. Name a few items of what to do before returning a reamer to the tool crib. 11. What should be done in the case of a broken or damaged reamer? 12. Where is the square on a hand reamer and for what is it used?

Reaming Through Holes

REAMING BY HAND

Reaming a hole is done to bring the hole to an exact size. For example: When fitting a straight pin to a hole where a snug fit is necessary, first drill the hole 1/64" to 1/32" smaller than the pin, and then

REAMING TAPER HOLES

It is always necessary to use a taper reamer to fit a tapered pin. (Fig. 60). The hole is first drilled about the size of the small end of the tapered pin and a taper reamer is then used to taper the hole to fit the pin. Use the same number taper reamer as the pin number. See Fig. 59, "b". Care must be used when reaming with a taper reamer or the hole will be reamed too large. A taper reamer is not like a straight reamer in one respect: One turn with a taper reamer can mean the difference between a good fit and a spoiled piece of work. For this reason it is safer to use a hand reamer on such jobs.

Fig. 59

Fig. 60

Never try to bring a hole to "position" with a hand reamer. The reamer follows the drilled hole. Trying to change the direction of the hole by leaning the reamer or applying more pressure on one side will be useless and may possibly break the reamer.

REAMING BY AIR MACHINE

Great care must be used when reaming very small holes by machine. The air machine is heavy, and the operator cannot easily get the "feel" of a small reamer to an extent which will prevent breakage. This is not so likely to happen with larger reamers. The job may be done much more quickly by using the air machine. Use a small machine for a small job.

When reaming with the air machine, keep the reamer "in line". Wobbling around on the start will affect the size of the hole. After the reamer has entered the hole, it must be kept in line to prevent breaking.

When the depth of the reamed hole is very great, more care must be taken. Reaming holes for dowel pins, or reaming holes through unit bases and foundations for fitted bolts calls for careful handling of the air machine and reamer.

GENERAL PROCEDURE

The general procedure for reaming holes through a base and foundation is as follows:

NOTE: A generator base frequently has 7/8" drilled holes in the corners when it is delivered by the manufacturer. The other holes in the base are about 1" drilled and not reamed, and a black iron bolt of the proper size is used to bolt the unit at these places.

Fig. 61

1. With the proper size drill in the "corner air drilling machine" drill the foundation on the corners, using the drilled hole in the base of the unit as a guide. See Fig. 61.

NOTE: A corner air drilling machine (Fig. 62) is an air or electric motor driven device made especially for drilling in close corners.

2. If the corner hole is 7/8" diameter, run a 15/16" reamer through, after drilling the 7/8" hole.

Fig. 62

3. Now run a 1" reamer through, which will remove 1/32" stock on a side.

4. Mike the hole and order from the machine shop the right number of fitted bolts, .00025 per inch larger than the hole. This allows just the right amount for a drive fit.

NOTE: On some heavy installations the corner holes are reamed to 1.500 diameter, and the bolts are made 1.503" for a snug fit. In those cases a bushing is placed in the

Fig. 63

Fig. 64 Drilling a foundation, using the hole in the base as a guide and following the pilot hole in the foundation, Previously drilled through when the bushing in Fig. 63 was used as a guide.

Fig. 65 Reaming both holes through the base and the foundation with a straight reamer. The reamer follows the drilled hole. Keep the reamer vertical.

QUESTIONS

1. Explain what is meant by reaming "through holes".

2. State the procedure for drilling and reaming where a coupling must be prepared to couple two rods or shafts.

3. How is the drill size determined when drilling a hole that is to be reamed for a taper pin?

4. Compare the uses of a large drilling machine and a small drilling machine.

5. State which of the following size reamers should be used in a large drilling machine: 3/8" reamer, 1" reamer, 1/2" reamer, 1-1/2" reamer, 5/8" reamer, #2 taper reamer.

6. How much stock is allowed in the diameter of a hole for reaming?

7. Name the correct size drill to use when a hole must be reamed 15/16" diameter.

8. How is the size of a fitted bolt given to the shop when ordering a number of fitted bolts?

9. State the size to give the shop for fitted bolts which are to be used in 1-1/4" reamed holes.

10. If the holes in the pedestal are 1-1/2" diameter, what is the procedure for drilling the holes in the foundation?

11. What is the purpose of a pilot hole?

12. Explain the reason for using a spiral fluted reamer instead of a straight fluted reamer.

Using a Portable Air Drill

Fig. 66 -- Drilling With a Corner Machine

AIR MOTOR

An air motor "a", Fig. 67, maybe used for drilling, boring, reaming, grinding, and other operations that require the use of a portable rotating tool. One section of the handle is turned to start or stop the motor. The lead hose "b", (also called a whip), is a six-foot length of hose with one connection threaded to screw into the motor handle. On the other end is a universal hose coupling. In some instances the lead hose is wrapped with wire in order to reduce wear.

DESCRIPTION OF AN AIR HOSE

Air hose is constructed of braided cord and rubber. The rubber should be tough and oil-resistant. Universal air hose couplings are combination male and female, and are attached at each hose end. The air connection manifold is joined to a main air line and has two or more air hose connections. Each connection has a quarter turn cut-off.

RIGGING AN AIR MOTOR

To rig an air motor, screw the threaded end of the lead hose into the motor handle, couple the other end of the lead hose to one end of the air hose, and couple the other end of the air hose to manifold connection.

USING A DRILLING POST

A drilling post, commonly called "old man" is a tool used to assist the operator of a drill in forcing the drill through the material. See "k". Fig. 67.

The foot "L" is slotted lengthwise. A bolt is placed in this slot to clamp the foot to the material. The post "j" is screwed or welded into the foot. The arm may be raised and lowered on the post and clamped at any height or angle around the post by clamp bolt "n". The under side of the arm has many small counter sunk places to fit the tapered end of a drill feed post.

Fig. 68 Applying the "feed" with a Drilling Stick

USING A DRILLING STICK

Instead of using an "old man", a "stick" is used on many jobs to apply the feed to an air drill. Fig. 68 shows a stick in use.

The "stick" is made in the carpenter shop and sometimes will serve for several jobs. It should be laid away for future jobs until after repeated use it becomes unfit for service. Fig. 69 shows how the bolt is bent to act as one end of a clamp and placed through a convenient hole. See Fig. 69 at "t". The rod is put through the hole in the plate (See Fig. 70) as at "y" and raised to a vertical position as at "2". The nut is adjusted to the correct height to obtain the maximum pressure.

HOW TO SET UP A PORTABLE AIR DRILL

PROCEDURE (Applicable to most jobs)

1. Place the foot "L" across the hole on top of the plate. See Fig. 67. 2. Clamp the foot to the plate, using a "C" clamp or other clamping device. If there is a convenient hole in the plate, use it. NOTE: Place bolt "o" through the slot in the foot and the hole in plate and tighten it securely. This clamps the "old man" to the plate. When a "C" clamp will not reach and there are no holes which may be used for bolting down, tack-weld a bolt to the plate for clamping down the foot of the "old man". See that the weld is removed after the job is finished.

Fig. 69

3. Place the drill in position to drill the hole.

4. Swing the arm around over the top of the drill and fit the tapered end of the feed post into a countersunk hole in the arm. The arm has many of these and the one that lines up with the feed post is the correct one. If a hole in the arm does not line up with the tapered end of the feed post, move the foot "l" to bring a convenient hole into a vertical line with the point of the drill. See Fig. 66.

Fig. 70

5. Clamp the arm in position with clamp bolt "n".

6. Turn the feed wheel and press the drill firmly into place.

7. Oil the drill point and start drilling.

8. Turn the feed wheel slowly while the drill turns, until the hole is drilled. Turn the feed wheel and press drill firmly in place. Check to see that drill lines square with work.

QUESTIONS

1. Explain the reason for using an air drill.

2. State the reason for using an "old man" with an air drill.

3. Name the several parts of an air drill.

4. For what purpose is the foot of the "old man" used?

5. Explain how the feed is applied to the drill when using an air drilling machine.

6. Is the foot of the "old man" tack welded to the plate or deck when convenient bolt holes may be used?

7. What is understood by the term "drilling stick"?

8. Explain the difference between a "corner drilling machine" and an ordinary air drill.

9. Where is a corner drilling machine used? Why?

10. How is the drill secured in the air drill chuck?

11. Why is there a flat surface on the taper shank of a drill?

12. For what purpose is a sleeve used in an air drill chuck?

13. What precautions should be observed when using a small drill in an air drill?

14. Describe the correct procedure and state what equipment is used when using a drilling stick and an air drill.

15. State the reasons for applying lubricating oil to the work when drilling a hole.

* Adapted from "Shipyard Outside Machinist," by State Department of Education, Alabama.

Threading Bolts and Nuts

STANDARD SCREW THREADS

In order that all bolts and nuts may fit other bolts and nuts, wherever they may be made, a certain number of threads is always cut on the same diameter bolt or inside the nut. A table of the more commonly used threads for bolts and nuts is given below:

American Standard Screw Threads, N. C.

BOLT	THREADS	SIZE DRILL	SIZE ACROSS
SIZE	PER INCH	FOR HOLE	FLAT OF NUT
1/4	20	13/64	1/2
5/16	18	1/4	19/32
3/8	16	5/16	11/16
7/16	14	23/64	25/32
1/2	13	27/64	7/8
9/16	12	15/32	31/32
5/8	11	17/32	1-1/16
3/4	10	41/64	1-1/4
7/8	9	3/4	1-7/16
1	8	55/64	1-5/8
1-1/8	7	31/32	1-13/16
1-1/4	7	1-3/32	2
1-3/8	6	1-7/32	2-3/16
1-1/2	6	1-11/32	2-3/8
1-5/8	5-1/2	1-27/64	2-9/16
1-3/4	5	1-17/32	2-3/4
1-7/8	5	1-21/32	2-15/16
2	4-1/2	1-49/64	3-1/8
2-1/4	4-1/2	2-1/64	3-1/2
2-1/2	4	2-15/64	3-7/8
2-3/4	4	2-31/64	4-1/4
3	3-1/2	2-11/16	4-5/8
3-1/4	3-1/2	2-15/16	5
3-1/2	3-1/4	3-11/64	5-3/8
3-3/4	3	3-3/8	5-3/4
4	3	3-5/8	6-1/8
4-1/4	2-7/8	3-27/32	6-1/2
4-1/2	2-3/4	4-3/32	6-7/8
4-3/4	2-5/8	4-5/16	7-1/4
5	2-1/2	4-9/16	7-5/8
5-1/4	2-1/2	4-13/16	8
5-1/2	2-3/8	5-1/32	8-3/8
5-3/4	2-3/8	5-9/32	8-3/4
6	2-1/4	5-1/2	9-1/8

NOTE: There are two series of American Standard Screw Threads. They are National Fine (N. F.) and National Coarse (N. C.). The National Coarse threads are generally used in Commercial shipyard work. Both series are derived from the United States Standard. (U. S. S.).The U. S. Navy uses Navy Standards.

For Commercial shipyard work the size of the opening in a wrench is based on the diameter of the bolt multiplied by 1-1/2 plus 1/8 inch. For example: The size of the wrench opening for a 1/2 inch nut is 1/2 x 1-1/2 3/4. Adding 1/8 inch gives 7/8 inch as the size of the nut across the flats. The U.S. Navy standard opening in a wrench for a 1/2" nut is the diameter of the bolt multiplied by 1/2. For example: 1/2 x 1-1/2 3/4. Note that nothing is added after the multiplication 3/4" is the size of the nut across the flats.

THE TAPER TAP is generally used to tap a hole in a nut or in a piece of work where the hole goes all the way through the metal. See Fig. 71. This tap may be used in a very deep "blind" hole. A "through" hole is drilled completely through, and a "blind" hole is drilled only part way through. A taper tap will "bottom" in a blind hole before a full thread is cut. See Fig. 72.

Use a PLUG TAP when tapping a blind hole. Run the tap in as far as , possible and back it out. Now use the bottoming tap, which will cut a thread all the way to the bottom of the hole. See Fig. 73.

CAUTION

Never force a tap. Remember they are hardened and will snap off

Fig. 71

Fig. 72

Fig. 73

easily if forced too hard. Be especially careful when approaching the bottom of a blind hole. Small taps will snap off much more quickly than the larger sizes. Getting a broken tap out of a hole is difficult and wastes a lot of time, sometimes spoiling the hole completely.

THREADING

Bolts and nuts from 1/4" diameter up to 1" diameter may be threaded by hand. The operation is performed by using a die, held in

Bolts and nuts are generally threaded in the machine shop and come to the job ready to assemble. However, it may be necessary to "chase" a thread on a damaged bolt. In this case the work is done in the shipyard, on the job.

CORRECT HANDLING OF THE TAP AND DIE

THE DIE: When starting to chase a thread on a bolt or rod, slightly taper or chamfer the end of the bolt or rod to give the die a chance to "start" straight. Better work will result from this practice. The die stock must be held square with the center line of the bolt or the thread will "run" to one side and make a bad job. The die will probably "take hold" after a couple of turns, and the bolt should be lubricated with a little white or red lead.

After the die is on far enough for the end of the bolt to show through, the die stock should be "backed" slightly to free the cuttings. This is done after every few turns. After the thread has been cut to the desired depth, reverse the direction of the die and run it off.

THE TAP: When starting to tap a hole, keep the tap square with the face of the work, or if the hole is on a slant, keep the tap square with the center line of the hole. After three or four turns, check the direction of the tap by "sighting" from front and side. If satisfactory, go ahead. If the tap "leans", bear slightly on the tap to bring it back straight. Be careful to bear easy or the tap will break. When tapping holes, dip the tap in white or red lead. Lead is heavier than cutting oil and will make a smoother thread. Lard oil is often used when lead is not available.

TAP SETS

Hand taps are made in sets of three: Taper--tapered for 5 of 6 threads Plug--tapered for 3 or 4 threads Bottoming--corners of leading threads chamfered

PIPE THREADS

Pipe thread taps and dies are entirely different from screw thread taps and dies. Pipe threads are tapered. When it becomes necessary to cut pipe threads or to tap holes for pipe fittings, the mechanic should consult a standard table which may be found in most tool rooms, or foremen's offices.

PROCEDURE

1. Check the size of the tap to be used. The blueprint usually gives the information. If there is no blueprint, check the number of threads on the bolt. See Fig. 74 and Fig. 75 for getting the pitch of the thread. Measure the O.D. of the bolt.

3. Use a few drops of cutting oil or white lead on the tap if the material is steel.

NOTE: Use a "dry" tap when tapping cast iron. A little white lead on the shank-end of the tap threads will make the tap work easier in the threads already cut. For brass and copper use turpentine and lard oil. For aluminum use kerosene and lard oil.

Fig 75

4. Start the tap square with the work.

5. After two or three turns, "sight" the tap for direction. If satisfactory, proceed.

6. After one or two more turns, back the tap about half a turn and free the chips. Start ahead again.

7. Repeat step 6 until the tapping is finished.

NOTE: Proceed the same way when tapping a blind hole, except for the use of two taps: plug and bottoming taps.

DIES

Hand threading dies come in three types:

1. Dies which are round and fit a round socket in the die stock. The outside diameters of the dies in a set from 1/4" up to 1/2" are the same. Then the next series from 9/16" up may be a larger outside diameter. These round dies are adjustable by means of a screw in the die stock.

2. Dies which are square and in one or two pieces. The two halves of some dies may be adjusted by means of a screw in the die

3. Dies which are square and not adjustable (See Fig. 76) are held in a square stock by means of a thumb screw. All dies in one series are the same size outside. The threaded portion of the die may run from 1/4 - 20 up to 1-1/2 - 6, in series to suit the capacity of the stock and handle. The larger the diameter of the bolt, the more the leverage required to turn the die on the bolt; therefore, longer handles are used on die stocks for large dies.

ADJUSTING THE DIES

Fig 76

In using any type of die, the operator may thread the bolt to fit the nut very snugly or very loosely. This is done by placing a good tap in the die and adjusting the die (if it is adjustable) to fit the tap with the desired clearance. The instructor will demonstrate how this is done. NOTE: This type of square die has four thread chasers inserted. The chasers are made of high grade tool steel for long wear. See Points "a".

QUESTIONS

1. What is meant by the word "standard" when applied to bolt and nut threads: Commercial? U. S. Navy?

2. State the rule for finding the size across the flat of a nut.

3. What is the dimension across the flat of a 1/2" nut: Commercial? U. S. Navy?

4. Explain what is meant by "tapping" a hole.

5. What tool is used to "chase" a thread on a bolt?

6. Name the three taps generally found in one set.

7. What is understood by the term "blind hole"?

8. Which tap is used for tapping a "through" hole?

9. Why must the tap be started square with the work?

10. What lubricant is used for tapping cast iron?

11. Why is the tap "sighted" for direction after the first few turns?

13. Explain the advantage of using white lead on the shank end of the tap when tapping cast iron.

14. Give the pitch of a thread which numbers 16 threads per inch.

15. What is the pitch of a 1" inch diameter bolt, American Standard thread?

16. What is the difference between standard screw threads (National Standard) and Pipe threads?

17. Where may the information be found for the size of the hole to drill for a 3/8" pipe thread?

Tightening a Stud in a Threaded Hole

INFORMATION

Figure 78 shows a stud driver used to tighten a stud (Fig. 77) in a threaded hole. The stud driver is made by drilling and tapping a piece of hexagon or square material to fit the stud on one end and to fit a set screw on the other end.

Installing this stud with a pipe wrench would offer a possibility of spoiling the threads or damaging the body of the stud because the smooth portion between the threads is so short that the wrench jaws would overlap too much.

Fig. 77

Fig. 78

Binding the stud fast in a hexagon piece of stock, as shown, by means of a heavy cap screw, permits the use of a large wrench on the hexagon stock to run the stud home securely.

TIGHTENING A STUD IN A THREADED HOLE

PROCEDURE

1. Examine the threaded hole to determine the size and number of the threads. If uncertain, check for number of threads with the thread gauge.

Fig. 79

NOTE: A thread gauge is a tool which is put up in much the same form as a thickness gauge except that each leaf is notched out on one edge to match the thread on some particular screw. See Fig. 79. A screw, stud, or bolt may be tried in a threaded hole or in a nut to determine the "pitch" of the thread. "Pitch" is another name for the spacing of the threads on a bolt or in a nut.

2. Check carefully to see if the threads in the hole have been battered or mashed. If necessary, retap the hole with the proper size tap.

3. Dip the hole end of the stud in white lead or other lubricant. Engine oil is sometimes used, and in specific jobs a mixture of graphite and oil is used. Lubrication of the threads prevents corrosion and makes the stud easier to remove when necessary.

4. Screw the stud in the hole hand-tight. Use care that the fingers are not cut on the stud threads.

5. Screw the stud driver up on the stud to a length of about times the diameter of the thread.

6. Using the open end wrench, tighten the set screw or locking stud against the stud.

7. With an open end wrench that fits the body of the stud driver, tighten stud firmly in the threaded hole. Use judgment in tightening the stud so that it is not broken off due to too much strain.

NOTE: In removing a stud that is hard to start with a stillson wrench, two nuts may be tightened together on the end of a stud. The stud is removed with an open end wrench placed on the nut nearest to the stud hole.

QUESTIONS

1. Why is a set screw used in a stud driver?

2. To what depth is the stud driver screwed on the stud?

4. Explain how a threaded hole is examined for fitting a stud.

5. What two precautions must be taken when placing a stud in a threaded hole?

6. How is the correct number of threads per inch determined?

Removing Studs or Broken Bolts

HOW STUDS OR BOLTS BECOME BROKEN OFF

Removing old studs or bolts in the course of overhauling various pieces of equipment is sometimes very difficult. The threads are rusted, and the stud or bolt may break under the strain of turning it out of the threaded hole. If the broken portion remaining in the tapped hole projects far enough, a pipe wrench may sometimes be used and the broken piece backed out. When the wrench fails, two nuts may be locked on the threaded end of the stud which projects, and the stud may be backed out. This is only possible where there is enough thread left o