midterm 1 Flashcards
(166 cards)
1
Q
What is the primary piece of safety equipment in machine shop?
A
Eye protection equipment
2
Q
What are side shields and what are they designed to do?
A
The side shield protects the side of the eye from flying particles.
3
Q
What can be done to control grinding dust?
A
Dust vacuums, coolants for grinding dust, wearing a respirator
4
Q
What hazards exist from coolants, oils, and solvents?
A
Slipping hazards, fire hazard, breathing hazard.
5
Q
Describe proper lifting procedure.
A
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.
6
Q
- Describe at least two compressed-air hazards
A
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.
7
Q
- Describe good housekeeping procedures.
A
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.
8
Q
- Describe the purpose of lockout/tagout procedures.
A
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.
9
Q
- How should the workpiece be prepared prior to layout?
A
Burrs should be filed off. The part should be cleaned then inked.
10
Q
- What is the reason for putting the workpiece on a paper towel?
A
So that die does not spill onto the table.
11
Q
Define the term pitch diameter.
A
pitch is the distance between major and minor diameter. from the peak to the valley of the thread.
12
Q
Name two ways to measure a thread.
A
Thread micrometer or three wire thread measurement.
13
Q
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.
A
the minum amount of threads is as much as the screw diameter.
14
Q
describe when class two fits are used.
A
Class 2 theads are found on most screws, nuts, and bolts used in the manufacturing industry.
15
Q
describe UNC and UNF
A
UNC stands for United national coarse thread.
UNF stands for United National Fine thread.
16
Q
What is the formula for calculating the OD of a machine screw?
A
the formula is D= “number of the machine screw” X .013in + 0.060in; D=8 X .013 + .06 =. 164
17
Q
what are setscrews used for?
A
setscrews are used to secure gears or pullys to a shaft.
18
Q
Describe the strength classification system and marking for bolts.
A
the strength of bolts is marked by the marking on the head. the grade indicates the strength of the fastener.
19
Q
when are stud bolts used.
A
used instead of long bolts used to aid in assembly of heavy parts by acting as guide pins.
20
Q
two reasons why flat washers are used.
A
they provide a larger contact area for the bolt or nut.
21
Q
what is the purpose of a helical spring lock washer.
A
prevents the unplanned loosening of a nut or bolt
22
Q
when is a internal-external tooth lock washer used
A
are used on over sized holes or to provide a larger bearing surface.
23
Q
when are dowel pins used
A
to align two or more parts.
24
Q
when are taper pins used.
A
accurate align parts that need to be dissembled often.
25
when are roll pins used.
used to align parts. holes that recieve thses pins do not need to be reamed.
26
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.
27
what is the purpose of a key
they transmit the power between the shaft and the pully.
28
When is a Woodruff key used.
they are used where only light loads are used.
29
when are Gib head keys used
they are used to transmit heavy loads.
30
1. 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.
31
2. 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.
32
3. 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.
33
4. 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.
34
5. 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.
35
6. 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
36
7. 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.
37
8. How is the machinist’s bench vise measured for size?
It is measured by the width of the jaws.
38
9. Explain two characteristics of the insert jaws on vices?
the insert jaws are hard and they have a grip patern cut into them
39
10. 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.
40
11. 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.
41
12. 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.
42
13. 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.
43
14. 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.
44
15. 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.
45
16. 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.
46
17. What is the kerf?
The kerf is the thickness of the cut produced by the saw.
47
19. 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.
48
20. 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.
49
21. What are four different cuts found on files?
Files are manufactured in single, double, curved tooth, and rasp cuts.
50
22. 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.
51
23. 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.
52
24. 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.
53
25. How is a hand reamer identified?
there is a square on the end of the shank. They have a long starting taper.
54
26. 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.
55
27. 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.
56
28. 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.
57
29. How much reaming allowance is left for hand reaming?
the preferred allowance is between 0.001 and 0.005”.
58
30. What type of tap is used to produce threads that extend almost to the bottom of a blind hole?
a bottoming tap.
59
31. 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.
60
32. 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.
61
33. How are taper pipe taps identified?
they are identified by the markings on the tap which say it has a ¾” taper per foot.
62
34. What kind of tools are used to drive taps when hand tapping?
A hand tapper a tapping wrench and a t-handle tapping wrench.
63
35. 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.
64
36. When should tap drill holes be reamed?
when an exact size hole is needed for tapping. Or if a hole needs to be round.
65
37. 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.
66
38. What causes rough and torn threads?
lack of cutting oil, not removing the chips from the tap, or a dull tap.
67
39. What causes oversize threads in a hole?
buildup on the cutting edges, misalignment in the tool holder or clamp. A misalignment in the spindle. And an oversized tap.
68
40. Give three methods of removing broken taps from holes?
a pair of pliers, a tap extractors, and using a EDM to remove the tap.
69
41. What is a die?
a thread cutting die is used to cut external threads on a shaft.
70
42. What tool is used to drive a die?
a diestock holds the die and is used to drive the die.
71
43. Where are hexagon rethreading dies used?
they are used to recut threads that have been damaged or are rusty.
72
44. Why do dies have a chamfer on the cutting end?
they have a chamfer so it is easier to start the threads when cutting and it distributes the force over more threads.
73
45. Why are cutting fluids used?
they are used to get a good smooth surface finish and to preserve the life of the tool.
74
46. What diameter should a rod be before being threaded?
a rod should be two to five thousands under sized.
75
47. Why should a rod be chamfered before being threaded?
to make the starting of the threads easier and to protect the first thread of the rod.
76
48. What is the primary function of the pedestal grinder in a machine shop?
to shape and sharpen tools.
77
49. Why should a tool grinder never be used for rough grinding metal?
because it will wear the grinding disc unevenly making it round or grooved and wear the disc down faster.
78
50. When a wheel needs to be reshaped, sharpened, and to some extent trued, what tool is used on a pedestal grinder?
a Desmond dresser is used.
79
51. Name at least three safety factors to remember when using the pedestal grinder
safety glasses should be worn. The wheel should be checked to make sure it is in good shape and the right one for the job. No lose clothing or long hair should be close to the wheel while it is running. Make sure all of the guards are in their proper place before operating.
80
52. What is the purpose of the wheel blotter?
it is a paper disc on the side of the wheel that marks what the wheel is made from and the coarse. Also it provides a barrier between the wheel and the bolt on the grinder
81
53. What is the primary safety consideration when selecting a grinding wheel?
the primary safety consideration is to do a ring test on the disc to check if it is cracked or chipped. If it is cracked or chipped it may break apart while spinning and be a major safety hazard.
82
54. What does the wheel ring test do?
A ring test lets the operator know if there are any cracks in the grinding wheel and if it is safe to use.
83
1. 35 mm =
1.37795 in
84
2. 125 in =
3175.00635 mm
85
4. Express the tolerance +/- .050 in metric terms to the nearest mm.
+/- 1.27 mm
86
5. To find centimeters knowing millimeters, (multiply/divide) by 10.
To convert millimeters to centimeters, divide by 10.
87
6. Express the tolerance +/- .02 mm in terms of inches to the nearest
1/10,000 in.
+/- 0.0008 in
88
7. What is meant by SI?
The International System of Units
89
8. Describe methods by which conversions between metric and inch measurement systems may be accomplished.
Conversion charts.
Conversion calculators can switch the measurements.
Most DRO’s can switch between easily.
CNC machines can work in both.
You can use the conversion formula (0.03937 in = 1 mm)
90
9. How large is a yard compared to a meter?
A yard is slightly smaller than a meter.
| 1 yard =3600/3937meter
91
10. Can an inch machine tool be converted to work in metric units?
Yes, if it has a DRO or is a CNC. And if it has the right dials others wise no.
92
1. Why should a micrometer be kept clean and protected?
Getting any fluid or chips into the micrometer can gum it up and it won’t be accurate. If it is dropped, the measurements can be thrown off and the micrometer won’t read accurately.
93
2. Why should a micrometer be stored with the spindle out of contact with the anvil?
If there is any moisture on the ends they can cause corrosion and make the micrometer read inaccurately.
94
3. Why are the measuring faces of the micrometer cleaned before measuring?
They are cleaned because fibers or dust can get stuck in-between the micrometer and the part being measured causing it to be wrong.
95
4. How precise is the standard micrometer?
The standard micrometer is accurate to 0.001”
96
5. What affects the accuracy of a micrometer?
Cosign error can be caused by not holding the micrometer correctly on the part. Proper care of the micrometer. The build quality of the micrometer.
97
6. What is the difference between the sleeve and thimble?
The sleeve is stationary with the lines each equaling .025”. the thimble is the cylinder that rotates around the sleeve and has hash marks for every .001”.
98
7. Why should a micrometer be read while it is still in contact with the object to be measured?
Because it eliminates the variable of the measurement being thrown off if the micrometer is removed improperly.
99
8. How often should an object be measured to verify its actual size?
The more the better. A minimum of two times.
100
9. What effect has an increase in temperature on the size of a part?
The size of the part will increase as the operation heats up the part.
101
10. What is the purpose of the friction thimble or ratchet stop on the micrometers?
It works like a turuq wrench and allows for equal pressure to be applied to each measurement making them more accurate.
102
1. Define Comparison Measurement
A device that has no capacity to show measurement is used to hold a length and then a tool that can measure is used to measure that.
103
2. What can be said of most comparison measuring instruments?
Most of them will reduce reliability.
104
3. What is cosine error?
Cosine error is when the measuring tool is not perpendicular with the surface being measured. Basically the measuring instrument is held at an angle to the part or vise versa.
105
4. How can cosine error be reduced?
By using proper equipment and technique.
106
5. What comparison measuring device is appropriate for measuring:
a. A milled slot that is 2 in wide with a tolerance of ±.002:
An adjustable parallel would be used.
107
5. What comparison measuring device is appropriate for measuring:
c. Checking the accuracy of a combination square:
A combination square can be checked for accuracy against a precision square or a precision block. A Cylindrical square is often used to check the accuracy of squares as well.
108
5. What comparison measuring device is appropriate for measuring:
d. The diameter of a 1-1/2” hole
A telescoping gage to hold the inside diameter and an outside micrometer to measure the telescoping gauge.
109
5. What comparison measuring device is appropriate for measuring:
e. The thickness of a shim under a piece of machinery:
A thickness gauge can be used to check the thickness of a shim. Maybe a height gauge that is calibrated with the end flipped upside down if it is too big.
110
6. What is a wringing interval?
The wringing interval is the space between wrung gage blocks.
111
7. Why are wear blocks used with gage blocks?
Wear blocks are used on applications with direct contact. Wear blocks are made from tungsten steel and are harder so they last longer.
112
8. What gage blocks are required to assemble the following stacks:
a. 3.0213, without wear blocks
0.1003-0.121-0.8-2.0
113
8. What gage blocks are required to assemble the following stacks:
b. 1.9643, with wear blocks
0.050-0.114-0.1003-0.8-1.0
114
9. Describe at least two gage block applications:
One is used to set the height of the triangle on a sign bar.
They are used to set other measuring equipment like snap gauges.
115
10. Name two angular measuring instruments with one degree of discrimination:
Plate protractors, bevel protractors.
116
12. How do 10 inch and 5 inch sine bars affect the height of gage block stacks?
To get the same angle on a 10 in block as you do on a 5in block the height of the gage blocks need to be doubled.
117
13. Calculate the stack size required for a 5 inch sine bar for the following angles:
a. 35 degrees:
2.868”
118
13. Calculate the stack size required for a 5 inch sine bar for the following angles:
b. 23.5 degrees:
1.994”
119
14. Why are tolerances important in manufacturing?
Tolerances are important because there is no such thing as a perfect part especially in production. Tolerances are the amount a part is allowed to be off by in order to be acceptable.
120
15. What are typical standard tolerances?
Tolerances are print specific. If no tolerance is specified, then the number of decimal places determines the tolerance. Fractions are +- 1/64. Two decimal = +- .010 three decimal = +- .005 four decimal = +- .0005 and angles +- ½ degree.
121
16. Name three geometric specifications called out on drawings?
Straightness, flatness, cylindricity.
122
17. Describe shrink and expansion fits:
When metal is heated it expands and when it is cooled it contracts. These fits can be used to lock something together like a shaft and collar the shaft and coolar are machined to be to big to fit together at room temp and then the shaft is cooled to shrink it and the collar is heated to be expanded and then they are pushed together. When they adjust to room temp they are held together with tremendous force.
123
18. What is the difference between bilateral and unilateral tolerances?
Bilateral tolerances are both plus and minus a tolerance dimension. Where unilateral tolerances are only allowed to be off one directon ither larger or smaller of the given direction.
124
19. What are high and low limit tolerances?
High and low limit tolerances are how much bigger or smaller the part can be.
125
20. For the dimension 2.467 +.001/-.003, what is the largest acceptable size?
2.468
126
21. What are overlapping tolerances?
Overlapping tolerances are for parts that need to fit together and having them to big or to small even though within tolerance can cause them to not fit together.
127
1. How should the workpiece be prepared prior to layout?
Burrs should be filed off. The part should be cleaned then inked.
128
2. What is the reason for putting the workpiece on a paper towel?
So that die does not spill onto the table.
129
3. Describe the technique of using the layout punch.
(prick punch?) hold at an angle and slide gently until it stops on the cross hairs of the scribe line, stand up stright and hit it on the head once with a hammer.
130
4. Describe the use of the combination square and rule in layout.
The Combination square is used with the rule in it to set a hash mark on each end of the part then the rule is set between the two hash marks and a line scribed between the two.
131
5. Describe the technique of setting a divider to size using a rule.
Place one side of the divider on the first hash mark on your ruler, and the other side on the hash marking your radius.
132
6. List three types of scribers.
Pocket scriber
Engineer’s scriber
Machinist’s scriber
133
7. Why does a square tool bit make a good scriber?
It works well for scribing along a rule.
134
8. Describe the use of the optical center punch.
The optical center punch has a magnifier glass on it to see the tip in relation to the hash marks. The locater is placed over the location and the galss is inserted, the locater in magnetized so it won’t move. The glass is swapped with the punch and hit with a hammer to make the prick.
135
9. Why are engraved rules best for setting dividers?
Because you can put the tips of the divider in the hashes.
136
10. What is the difference between a center punch and a prick punch?
A Prick punch is sanded at a sharper angle making and makes a more narrow hole. The center punch is sanded at a wider angle and makes a wider hole that is easier to drill.
137
3. Describe the procedure for checking the zero reference.
Clean the table, the base of the height gauge, and the tip of the gauge. Slide the scribe down till its on the table, set the zero on the gauge by moving the Vernier to line up with zero on the beam.
138
4. How can the zero reference be adjusted.
By moving the Vernier scale in relation with the beam.
139
6. What is the measuring range of a typical height
| gage?
10-72 inches.
140
7. When laying out angles, what tool is used in conjunction with the height gage?
A sine bar is used to scribe angles.
141
1. In what way do tool rakes, positive and negative, affect surface finish?
Negative rake tools are stronger and have longer tool life. They produce poor surface finish at low cutting speeds and good surface at high speeds. Positive rake tools are freer cutting at low speeds and produce good finishes when sharpened.
142
2. Soft materials tend to pressure weld on the top of the cutting edge of the tool. What is the condition called and what is its results?
it produces a built up edge and causes friction between the cutting edge and part resulting in a rough edge.
143
3. Which indicate a greater disruption of the surface material: thin uniform chips or thick segmented chips?
thin uniform chips.
144
4. What effect does cutting speed have on surface finish? On surface disruption or grain structure?
fast cutting speed will produce a smoother surface finish.
| The grain structure will not be distrupted at higher speeds.
145
5. Which property of metals is directly related to machinability? How do machinists usually determine this property?
the property of metals related to machinability is hardness. They test it with a file.
146
6. Define machinability.
Machinability is how difficult it is to machine a material based on tools, power consumption and surface finish.
147
7. If the cutting speed for low carbon steel is 90, and the formula for rpm is (CS X 4) / D, what should the rpm of the spindle of a drill press be for a 1/8-in. diameter high speed twist drill? For a .750- in. diameter drill?
for 1/8=2880rpm
| For .75= 480
148
8. If the two drills in question are used in a lathe instead of a drill press, what should be the rpm of the lathe spindle be for both drills?
for 1/8=2880rpm
| For .75= 480
149
9. Are feeds on a drill press based on inches per minute or inches per revolution of the spindle?
(IPR) inches per revolution
150
10. Which roughing feed on a small lathe would work best, .100 or .010 in. per revolution?
.010 in. per revolution
151
11. What kind of machine tool bases feed on inches per minute instead of inches per revolution?
milling machines are based on inches per minute.
152
12. What are the basic functions of a cutting fluid?
cooling and lubrication.
153
13. When a cutting fluid becomes rancid and odorous, what should be done?
the system should be flushed and new clean fluid should be added.
154
14. What method of applying cutting fluid is often used on a small drill press?
usually a pump oiler or a applying by hand with a bottle or can.
155
15. What kind of cutting fluid accessories are provided on most machine tools, lathes, milling machines, drill presses, and grinding machines?
a tank, a pump, and a nozzle with a hose.
156
16. What effect does increasing the cobalt content have on cemented carbides?
increasing the cobalt in cemented carbides lessens the hardness and increases the toughness.
157
17. How can you identify normal wear on a carbide tool?
it is chipped on the cutting edge.
158
18. What effect does the addition of titanium carbides have on tool performance?
Titanium carbide is used when resistance to cratering and deformation is required when machining steels.
159
19. What change in tool geometry can make possible an increased rate of feed with equal surface finish quality in turning operations?
having a larger radius on the end of the tool can help produce equal surface finish at higher speeds.
160
20. How does increasing the nose radius affect tool strength?
having a larger tool radius makes the tool stronger.
161
21. What is the hazard in using too large a nose radius?
It can cause chatter between the tool and work piece.
162
22. What are ceramic tools made of?
they are primarily made from aluminum oxide.
163
23. When should ceramic tools be used?
they are much harder than carbide so should be used if carbide fails. They should be used in high speed machines and with extremely ridged tool and machine setup.
164
24. Extremely hard or abrasive materials are machined with diamond tools. Is the material removal rate high? What kind of finishes ae produced?
only small removal rates are possible with diamond. The a good finish is produced at high speeds.
165
25. Polycrystalline diamond tools are similar to ceramic inserts. What is their major advantage?
they are more effective at machining abrasive materials that wear out other tool materials.
166
26. When sharpening brazed carbide tools should you use an aluminum oxide wheel or a silicon carbide wheel?
a silicon carbide wheel should be used to sharpen carbide. The shank is usually steel and can be ground with an aluminum oxide wheel.
