midterm 1 Flashcards
What is the primary piece of safety equipment in machine shop?
Eye protection equipment
What are side shields and what are they designed to do?
The side shield protects the side of the eye from flying particles.
What can be done to control grinding dust?
Dust vacuums, coolants for grinding dust, wearing a respirator
What hazards exist from coolants, oils, and solvents?
Slipping hazards, fire hazard, breathing hazard.
Describe proper lifting procedure.
Keep back straight while bending and lifting with your knees. Your rear should point downward and your knees up. Do the work with your legs, not your back.
- Describe at least two compressed-air hazards
One is while blowing your self off, too much air can push metal chips into your skin or air into your ear can cause you to lose hearing. Second is if the hose brakes it will flop around wildly, blowing dirt and metal chips everywhere that can hit other workers or cause a trip hazard.
- Describe good housekeeping procedures.
keeping the machine and floor around the maching clean and clear of stock and chips. Cleaning the coolant or oils off the floor with floor dry and disposing of oiled rags and solvent rags properly.
- Describe the purpose of lockout/tagout procedures.
The purpose of lockout/tagout is to prevent any power to or operation of the machine while it is being repaired so that mechanics can do their job safely.
- How should the workpiece be prepared prior to layout?
Burrs should be filed off. The part should be cleaned then inked.
- What is the reason for putting the workpiece on a paper towel?
So that die does not spill onto the table.
Define the term pitch diameter.
pitch is the distance between major and minor diameter. from the peak to the valley of the thread.
Name two ways to measure a thread.
Thread micrometer or three wire thread measurement.
What is the rule of thumb for the length of internal thread to maximize the strength of the bolt. how may threads do you need for the bolt will snap instead of stripping when pulled.
the minum amount of threads is as much as the screw diameter.
describe when class two fits are used.
Class 2 theads are found on most screws, nuts, and bolts used in the manufacturing industry.
describe UNC and UNF
UNC stands for United national coarse thread.
UNF stands for United National Fine thread.
What is the formula for calculating the OD of a machine screw?
the formula is D= “number of the machine screw” X .013in + 0.060in; D=8 X .013 + .06 =. 164
what are setscrews used for?
setscrews are used to secure gears or pullys to a shaft.
Describe the strength classification system and marking for bolts.
the strength of bolts is marked by the marking on the head. the grade indicates the strength of the fastener.
when are stud bolts used.
used instead of long bolts used to aid in assembly of heavy parts by acting as guide pins.
two reasons why flat washers are used.
they provide a larger contact area for the bolt or nut.
what is the purpose of a helical spring lock washer.
prevents the unplanned loosening of a nut or bolt
when is a internal-external tooth lock washer used
are used on over sized holes or to provide a larger bearing surface.
when are dowel pins used
to align two or more parts.
when are taper pins used.
accurate align parts that need to be dissembled often.
when are roll pins used.
used to align parts. holes that recieve thses pins do not need to be reamed.
what are retaining pins.
they are used to hold bearings or seals in thier housing. they are spring loaded and usuallly sit in a grove.
what is the purpose of a key
they transmit the power between the shaft and the pully.
When is a Woodruff key used.
they are used where only light loads are used.
when are Gib head keys used
they are used to transmit heavy loads.
- What kind of arbor presses are made? What makes them different from large commercial presses?
There are two types of arbor presses made. One is hydraulic and one is mechanical. An arbor press is hand powered and provides the “feel” for the pressure that big commercial presses do not.
- List several uses of the arbor press.
The arbor press is used to press in and remove ball bearings, pins, shafts into hubs, and bushings. Basically anything with an interference fit that needs a lot of force to push together.
- A newly machined steel shaft with an interference fit is pressed into the bore of a steel gear. The result is the shaft is ruined beyond repair; the bore of the gear is also badly damaged. What are some of the things that could have caused this failure?
They were not machined to the proper tolerances. There wasn’t a chamfer machined on the bore and shaft. Oil was not used to prevent seizing of the two.
- The ram of an arbor press is loose in its guide and the pushing end is rounded off. What kind of problem could this cause?
this will cause an alignment problem when pushing in the shaft. The tool will not have a flat vertical surface to set against and will be pushed in at an angle.
- When pressing a shaft from the inner race of a ball bearing, where should the bearing be supported on the bolster plate of the press?
the bearing should be supported against the inner race only so no pressure is applied to the outer race in order to prevent it from splitting.
- Prior to installing a bushing with the arbor press, what two important steps must be taken?
first is to check the tolerance of the parts, take into factor the temperature of the parts. Then make sure a chamfer is cut onto both the shaft and bore to prevent misalignment and finally to use high pressure lubricant to prevent the two from seizing
- Name five ways to avoid tool breakage and other problems when using push broaches for making keyseats in the arbor press?
You can face the teeth of the broach toward the back of the press to allow for better support,
Proper alignment of the Broach.
Make sure the broach has clearance to go through the part to be cut.
Use proper lubrication like high pressure lubricant.
Make sure two or three teeth are in contact with the work.
Never use the broch to cut material harder than Rockwell C35.
- How is the machinist’s bench vise measured for size?
It is measured by the width of the jaws.
- Explain two characteristics of the insert jaws on vices?
the insert jaws are hard and they have a grip patern cut into them
- How can the finished surface of a part be protected in a vise?
It can be protected by using softer materials like wood, copper, aluminum or can be put between the jaw and the part to prevent damage to the finish.
- Name three things that should never be done to a vise
Newer hammer on the movable jaw, never use a cheater bar to tighten the vise, never apply excessive heat to the jaws.
- How should a vise be lubricated?
the vise should be taken apart and all of the old grease cleaned off, then new grease should be packed into the screw and thrust collars then reassembled.
- What is the purpose of a soft jaw?
they are used to provide better grip on soft metals and to protect the finish of the part.
- Parallel clamps are used for heavy duty clamping work, and C-clamps are used for holding precision setups. True or false?
false. Parallel clamps do not have a lot of holding power and are used to clamp smaller and more delicate work. C-clamps are used for heavy duty applications.
- What advantage does the lever-jawed wrench offer over other similar tools such as pliers?
The lever jawed wrench has greater holding power then pliers. It can be locked to hold something in place.
- What are two important things to remember about standard screwdrivers that will help you avoid problems in there use?
to use the right width and thickness blade for the screw being used. Never use the screwdriver as a chisel or a pry bar.
- What is the kerf?
The kerf is the thickness of the cut produced by the saw.
- Give four causes that make saw blades dull.
The blades can be dulled by too much pressure on the backstroke of the cut, sawing too quickly, and moving the saw without any or too much pressure on the cutting stroke.
- A hacksaw blade should not be used in a cut started with a blade that has been used. Why?
because the thickness of the kerf could be thinner due to the old blade being worn. This will bend the teeth on the new blade and flatten the new blade out as well.
- What are four different cuts found on files?
Files are manufactured in single, double, curved tooth, and rasp cuts.
- Which of the two kinds of files- single cut or double cut- is designed to remove more material?
a double cut is designed to remove more material.
- What causes a file to get dull?
a file becomes dull because of too much or too little pressure applied during the cutting stroke. And by not lifting the file off the part on the back stroke.
- How does the hardness of a workpiece affect the selection of a file?
a coarse file is used on soft materials because it provides more room for the material being removed to build up. A hard material needs a finer tooth file to allow more cutting edges.
- How is a hand reamer identified?
there is a square on the end of the shank. They have a long starting taper.
- What is the purpose of a starting taper on a reamer?
the majority of the cutting is done on the starting taper. It helps to keep the reamer aligned and straight when cutting.
- What is the advantage of a spiral flute reamer over a straight flute reamer?
spiral flutes will cut over a keyset or grove without chattering and they cut with a sheering action.
- What is the difference between an expansion and an adjustable reamer?
Expansion reamers are used when enlarging a hole slightly for a proper fit. It has an adjustment screw that allows the size of the reamer to be adjusted. An adjustable reamer has inserted blades. adjustments are made by adjusting the nuts that hold the blades in.
- How much reaming allowance is left for hand reaming?
the preferred allowance is between 0.001 and 0.005”.
- What type of tap is used to produce threads that extend almost to the bottom of a blind hole?
a bottoming tap.
- How are thread-forming taps different from conventional taps?
thread forming taps do not produce chips. They are more of a thread rolling and push the material into a thread form.
- Why are rake angles varied on taps for different materials?
the softer a material the larger the rake angle is needed. Harder and more brittle material needs a reduced rake angle.
- How are taper pipe taps identified?
they are identified by the markings on the tap which say it has a ¾” taper per foot.
- What kind of tools are used to drive taps when hand tapping?
A hand tapper a tapping wrench and a t-handle tapping wrench.
- Which three factors affect the strength of a tapped hole?
the strength of a tapped hole depends on the material being tapped, the percentage of full thread depth and the length of the thread.
- When should tap drill holes be reamed?
when an exact size hole is needed for tapping. Or if a hole needs to be round.
- What causes taps to break while tapping?
taps break because there are too many chips in the cutting flutes, not enough of or not the right cutting oil, spinning too fast, or the material is too hard.
- What causes rough and torn threads?
lack of cutting oil, not removing the chips from the tap, or a dull tap.
