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CHS Metal Manufacture Bench Work Data
Terms in this set (57)
What clamping position should be considered when mounting a vise on a workbench?
The vise should be positioned so that a long piece can be held vertically in the jaws without interference from the workbench.
Name two types of bench vises.
The solid base and the swivel base types.
How is the machinist's bench vise measured for size?
By the width of the jaws.
Explain two characteristics of the insert jaws on vises.
Insert jaws are hardened and have a diamond pattern or criss-cross serrations.
How can a finished surface be protected in a vise?
Copper, soft metal, or wood may be used to protect finishes from insert jaw serrations.
Name three things that should never be done to a vise.
"Cheater" bars should never be used on the handle. The movable jaw slide bar should never be hammered on, and excessive heat should never be applied to the jaws.
How should a vise be lubricated?
The vise should be taken apart, cleaned, and the screw and nut cleaned in solvent. A heavy grease should be packed on the screw and thrust collars before reassembly.
A 4-in machinist bench vise has jaws 4-in. wide. True or False?
What is the purpose of soft jaws?
The purpose of soft jaws is to protect finished work from being damaged by the hard serrated jaws. Also, soft jaws of leather or a softer metal are used for gripping soft metals.
Parallel clamps are used for heavy duty clamping work, and C-clamps are used for holding precision setups. True or False?
False. C-clamps are used for clamping work. Some heavy-duty types can hold many hundreds of pounds.
To remove a nut or bolt, slip joint or water pump pliers make a good substitute for a wrench when a wrench is not hand. True or False?
False. This practice can quickly ruin good machinery, so that the proper tool can never be used.
What advantage does the lever jawed wrench offer over other similar tools such as pliers?
The principal advantage of the lever-kawed wrench is its great holding power. Most types have hard, serrated jaws and so should not be used on nuts and bolt heads.
Would you use a 3-lb ball peen hammer for layout work? If not, what size do you think is right?
No. Hammers used for layout work range from 4 to 10 oz in weight. A smaller one should be used with a prick punch for delicate work.
Some objects should never be struck with a hard hammer - a finished machine surface or the end of a shaft, for instance. What could you use to avoid damage?
Soft hammers and mallets are made for this purpose. When setting down work in a drill press or milling machine vise, for instance, a lead hammer is best because it base no rebound.
A machine has a capscrew that needs to be tightened and released quite often. Which wrench would be best to use in this case: an adjustable or box wrench? Why?
The box type, either socket or end wrench, would be best, as it provides contact on the six points of the cap screw, thus avoiding the damage and premature wear that would be cause by using an adjustable wrench.
Why should pipe wrenches never be used on bolts, nuts, or shafts?
The hard serrated jaws will damage machine parts. Pipe wrenches should be used on pipe and pipe fitting only.
What are two important things to remember about standard screwdrivers that will help you avoid problems in their use?
Standard screwdrivers should have the right-width blade to fit the screw head. They should be shaped correctly and, if worn, reground and shaped properly.
What is the kerf?
The kerf is the groove produced in the work by a saw blade.
What is the set on a saw blade?
The set on a saw blade is the width of the teeth bent out form the glad back.
What is the pitch of the hacksaw blade?
The pitch of a hacksaw blade refers to the number of teeth per inch on a saw blade.
What determines the selection of a saw blade for a job?
The first consideration in the selection of a saw blade is the kind of material being cut. For soft materials use a coarse-tooth blade and for harder materials use a fine-pitch blade. The second point to watch is that at least three teeth should be cutting at the same time.
Hand hacksaw blades fall into two basic categories. What are they?
The two basic kinds of saw blades are the all-hard blade and the flexible blade.
What speed should be used in hand hacksawing?
Generally, a speed between 40 and 60 strokes per minute is suggested. It is best to use long and slow strokes utilizing the full length of the blade.
Give four causes that make saw blades dull.
Excessive dulling of saw blades is caused by pressure on the saw blade on the return stroke, sawing too fast, letting the saw slide over the workpiece without any cutting pressure, or applying too much pressure.
Give two reasons why hacksaw blades break.
Saw blades break if too much pressure is used or if the blade is not sufficiently tightened in the saw frame.
A new hacksaw blade should not be used in a cut started with a blade that has been used. Why?
When the saw blade is used, the set wears and makes the kerf cut narrower with a used blade then the kerf cut with a new blade. If a cut started with a used blade can't be finished with that blade but has to be completed with a new blade, the workpiece should be turned over and a new cut started from the opposite end of the original cut. A new blade used in a kerf started with a used blade would lose its set immediately and start binding in the groove.
What dangers exist when a hacksaw glad breaks while it is being use?
When a blade breaks, it shatters, causing blade particles to fly quite a distance with the possibility of injuring someone. Should the blade break while sawing, it may catch the operator off balance and cause him or her to push a hand into the workpiece while following through with the sawing stroke. Serious cuts or abrasions can be the result.
How is a file identified?
By its length, shape, cut, and coarseness.
What are the four different cuts found on files?
Single cut, double cut, curved cut, and rasp.
Name four coarseness designations for files.
Rough, coarse, bastard, second cut, smooth, and dead smooth
Which of the two kinds of files - single cut or double cut - is designed to remove more material?
The double cut file
Why are the faces of most files slightly convex?
To make it possible to file a flat surface by offsetting the tendency to rock a file. To compensate for the slight downward deflection when pressure is applied while filing. To concentrate pressure on fewer teeth for deeper penetration.
What difference is there between a blunt and tapered file?
A blunt file has the same cross-sectional area from heel to point, whereas a tapered file is larger at the heel than at the point.
What difference exists between a mill file and an equal-sized flat file?
A mill file is thinner than a comparable-sized flat file.
What is a warding file?
A warding file is rectangular in shape and tapers to a small point, making filing possible in narrow slots and grooves.
An American pattern file differs in what way from a Swiss pattern file?
Swiss-pattern files are more precise in construction; they are more slender and have teeth to the extreme edges.
What are the coarseness designations for needle files?
Coarseness is identified by numbers from 00 (fine) to 6 (coarse).
Why should files be stored so they do not touch each other?
Where files touch each other, teeth break off or become dull.
What happens if too much pressure is applied when filing?
Too much pressure will break teeth off of a file. It also will cause pinning and scratching of the work surface.
What causes a file to get dull?
Files in contact with each other, files rubbing over the work without any pressure being applied, filing too fast, or filing on hardened materials causes files to dull.
Why should a handle be used on a file?
As a safety precaution; an unprotected tang can cause serious injury.
Why should workpieces be measured often?
Measuring the workpiece for flatness and size ensures that the filing is done in the right place and that the filing is stopped before a piece is undersize. Measuring often is not a waste of time.
What happens when a surface being filed is touched with the hand or fingers?
Touching a workpiece is just like lubricating the workpiece or the the file so that it slips over the work without cutting. This also causes a file to dull quickly.
How does the hardness of a workpiece affect the selection of a file?
A soft workpiece requires a file with coarser teeth, because there is less resistance to tooth penetration. A fine-toothed file would clog up on soft materials. For harder materials use a fine-toothed file to have more teeth making smaller chips.
How can rounded edges be avoided when a workpiece is draw filed?
The draw filing stroke should be short enough that the file never slips over the end of the workpiece. Care should be taken that no hollow surface is created through too short a stroke.
Should pressure be applied to a file on the return stroke?
Pressure is only applied on the forward stroke, which is the cutting stroke.
Why is a round file rotated while it is being used?
Rotating a round file clockwise while filing makes the file cut better and improves surface finish.
How is the hand reamer identified?
Hand reamers have a square on the shank and a long starting taper on the fluted end.
What is the purpose of a starting taper on a reamer?
A reamer does its cutting on the tapered portion. A long taper will help in keeping a reamer aligned with the hole.
What is the advantage of a spiral flute reamer over a straight flute reamer?
Spiral-fluted reamers cut with a shearing action. They will also bridge over keyseats and grooves without chattering.
How does the shank diameter of a hand reamer compare with the diameter measured over the margins?
The shank diameter is usually a few thousandths of an inch smaller than the nominal size of the reamer. This allows the reamer to pass through the hole without marring it.
When are expansion reamers use?
Expansion reamers are useful for increasing hole sizes by a small amount.
What is the difference between an expansion and an adjustable reamer?
Expansion reamers can be adjusted only a small amount by moving a tapered internal plug. Adjustable reamers have a larger range of adjustment, from 1/32 in. on small diameters to 5/16 in. on large reamers. Adjustable reamers have removable blades. Size changes are made by moving these blades with nuts in external tapered slots.
What is the purpose of cutting fluid used while reaming?
Cutting fluids are used to dissipate the heat generated by the reaming process, but in reaming, cutting fluids are more important in obtaining a high quality hold surface finish.
Why should reamers not be rotated backward?
Reamers dull rapidly if they are rotated backward.
How much reaming allowance is left for hand reaming?
The hand reaming allowance is rather small, between only .001 and .005 in.
If you were repairing the lathe tailstock taper, you would use a ___ reamer.
Morse taper reamer.
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