Volume 3 Flashcards
(454 cards)
1
Q
How much carbon to High-C steels contain?
A
Between .5 and 1.05 percent.
2
Q
Describe high-speed steel.
A
High-speed steal belongs to a group of tool steels with excellent red hardness. They retain hardness at operating temperatures between 1,100 and 1,200 F.
High-speed steals contain depth hardness.
3
Q
What are the main alloying elements of high-speed steel?
A
tungsten (W), molybdenum (Mo), chromium (Cr), vanadium (V), and C.
4
Q
What are the two classes of high-speed steel identified by the American iron and Steel Institute (AISI)? Please describe them.
A
T and M.
The class designated by the letter T has tungsten as its main alloying element.
The class designated by the letter M has molybdenum as the principal alloying element.
5
Q
Describe cemented carbides.
A
Cemented carbides are chemical compounds of metals and C. They are harder and more wear-resistant than high-speed steel tools.
6
Q
How do you select the carbides for an operation?
A
When you select a carbide for an operation, first select the group for the material on which you’ll use it, and then select the grade for the amount of hardness you’ll need.
7
Q
Describe cemented carbide group 1.
A
Group 1 is known as the wear-resistant straight carbide grade. They are designed to resist edge wear, and contain straight carbide grade composed of W with Co binders.
These grades contain from 94 to 97 percent W, C, and Co.
The ones containing more Co are tough and shock resistant, which makes them ideal for heavy rough cuts.
The ones containing more W are hard and abrasive resistant, they are used to taking lighter finishing cuts.
This group is used for machining gray cast iron, 200-300 series stainless, high-temperature nonferrous alloys, and plastics.
Don’t use them to machine plain C and alloy steels. They crater the faces of the cutting tools.
8
Q
Describe cemented carbide group 2.
A
Group 2 is known as Crater-resistant carbide grades.
Titanium (Ti) increases crater resistance and helps keep the tool’s cutting edge from deforming at the temperatures and pressures that result from heavy cuts.
These are used for machining plain C steels, alloy steels, alloy cast irons, cast steels, marensitic stainless steels, ferritic stainless steels, and all tool steels.
9
Q
Titanium carbides?
A
These grades contain no W carbide. These have excellent crater and heat resistance, which permits you to use them at higher cutting speeds.
10
Q
Describe tantalum carbides.
A
Tantalum carbide contain small amounts of W as an alloy. These carbides have high abrasion resistance and regularly perform machining operations at temperatures above 2,000 F.
11
Q
Describe coated carbides.
A
Coated carbides have a cemented carbide insert, called the substrate, on which a thin coating of TiC, aluminum oxide, or titanium nitride has been deposited.
Coated carbides operate at higher cutting speeds than uncoated carbides without significant loss of tool life and, if they operate at the same cutting speeds as uncoated carbides, they last longer.
12
Q
Why are coated carbides only available as inserts?
A
Because the thin layer prevents them from being reground.
13
Q
What is sintering?
A
Sintering means to hold a material under high pressure at just below the melting temperature until it fuses into a solid mass.
14
Q
Describe ceramic and cermet cutting tools.
A
Ceramic cutting tools, also known as cemented oxide tools, I made by sintering fine grains of aluminum oxide into a dense structure.
Ceramic cutting tools are used in operations where carbides wear quickly, but they’re not intended to replace carbides. Ceramics can cut at high speeds and high operating temperatures, but they’re brittle so they won’t withstand shock.
15
Q
Why should you not use ceramics or cermets to Al or Al alloys?
A
Because the aluminium oxide in these tools reacts with the Al content in the metals, which may cause the tools and the metals to fuse together.
16
Q
Describe cubic boron nitride.
A
Cubic boron nitride cutting tools are almost as hard as diamonds.
17
Q
What is in cubic boron nitride? How is it made?
A
CBN cutting tools are a substrate of cemented carbide with an outside layer of CBN. The CBN is part of the tool.
18
Q
Describe diamond cutting tools.
A
Industrial diamonds, also known as polycrystalline diamonds, machine extremely hard materials.
They are used mainly for finishing tools because they are brittle and don’t do shock or high cutting pressures.
19
Q
What and why should you not use with polycrystalline diamonds?
A
They are not effective for machining cobalt or nickel, because these alloys can chemically react with the diamond and cause rapid tool wear.
20
Q
When performing ordinary turning (i.e. straight turning, facing), what side does the cutting?
A
The side cutting edge does the cutting.
21
Q
What does the nose on a lathe cutter do?
A
The nose of the it’s cutting tool connects the side cutting edge and the end cutting edge, and is a critical part of the cutting edge because it produces the finished surface in turning.
22
Q
On a lathe cutting tool what does the end Cutting Edge do?
A
The end cutting-edge actually provides the clearance for the side Cutting Edge to work.
23
Q
On a lathe cutting tool, what do the flanks of the tool do? And where are they located on the cutting tool?
A
They’re relieved to permit the cutting edges to penetrate into the material surface. They are located below the cutting edges on the sides of the tools.
24
Q
On a lathe cutting tool, what does the face of the tool provide?
A
The cutting tool face provides a surface for chip formation.
25
On a lathe cutting tool what effect does a too steep of a Shear angle do on the face of the cutting tool?
If the shear angle is too steep, the cutting tool tends to "dig" out the chip, which puts additional cutting pressure on the workpiece and the cutter.
26
On a lathe cutting tool, what happens if the shear angle is too shallow on the face of a cutting tool?
If the sheer angle is too shallow, the cutting tool forms a long, shallow chip, and it tends to ride on the cutting surface instead of forming and falling off.
27
Describe a lathe right-hand cutting tool and a left-hand cutting tool.
Right-hand cutting tool has the side Cutting Edge on the left when viewed from the shank. The tool cuts from right to left. A left-hand cutting tool has the side Cutting Edge on the right when viewed from the shank.
28
On a lathe cutting tool, what are the relief angles? What do they do?
The angles formed by the intersection of the cutting edges in the plane perpendicular perpendicular to the tool shank are called relief angles. These angles allow allow the cutting tool to penetrate the workpiece.
29
On a lathe cutting tool what relief angle do you use for General turning?
For General turning, use a 10 degree relief angle.
30
For different material how must you adjust the relief angles?
Harder materials may require a smaller relief angle, while softer materials cut more successfully with a larger relief angle.
31
What is the relief angle for cemented carbide cutting tools?
The relief angle for cemented carbide cutting tools ranges from 5 degrees to 12 degrees.
32
What is positive-rake angle and a negative-rake angle on a lathe cutting tool?
The positive-rake angle causes the face of the cutting tool to slant downwards towards the shank, while the negative-rake angle causes this surface to slant upward from The Cutting Edge toward the shank.
33
What is the advantage of using a positive-side rake angle cutter and a negative-side right angle cutter?
Positive-side rake angles require less cutting Force then a negative-side rake angle. Also, positive-side right angle tools generate less heat and have a longer tool life than negative-side right angle cutting tools.
The advantage of having a negative side rake angle and negative back rake angle is The Cutting Edge is stronger and can withstand more severe cutting loads than a positive side cutting tools.
Negative rake angles are common in disposable carbide cutting tools because the top and bottom edges on the cutting tools can be used as cutting edges. Negative rake angle cutting tools have twice as many cutting edges as a positive rake cutting tools, which have cutting edges on only one face of the insert.
34
What does the end cutting edge angle do on a lathe cutting tool?
Tge End cutting edge angle slopes away from the nose of a tool so it clears the finished surface on the workpiece when you cut with a side Cutting Edge.
35
Why do lathes tool bits have a nose radius on them?
The nose radius is an extension of The Cutting Edge. The reason the nose forms radius is to keep the cutting tool for making small grooves in the workpiece as it passes, and also to keep the end Cutting Edge from breaking down while under pressure.
36
What happens when your lathe tool bit has a too large of a nose radius?
If the nose radius is large, it an form a thin chip and may not penetrate the workpiece during the cut. A large nose radius also causes the tool to chatter during the cut.
Too large a nose radius causes chattering, while too small a nose radius causes the point to break down quickly.
37
What nose radius should you use for average turning operations?
For average turning operations, use a nose radius of 1/64 to 1/8".
38
There are two types of cemented-carbide lathe cutting tools, what are they?
Brazed-tip and indexable inserts.
39
For lathe cutting tools, there are negative and positive rake inserts. Which one do you use if you need a low cutting force?
If you need a low cutting force, use a positive rake angle.
| Like if you are machining thin wall material.
40
What do you consider when determining the side cutting-edge angle to use?
Use a side cutting-edge angle large enough to permit the tool to be eased into the work;this he;[s to protect the nose of the cutting tool as it enters and leaves the work.
41
How do you set up your tool on a lathe?
Hold carbide tools in a sturdy tool holder, with the amount of tool overhang just enough for chip clearance. Set the cutting tool exactly on center because, when it is above or below center, there won't be enough clearance for the cutting edges.
42
On a lathe, what happens when a cutting speed is too fast or slow?
A cutting speed that's too high causes rapid tool failure, while a cutting speed that's too low causes inefficient cutting action and low production rates. A feed that's too light causes tool rub, which work-hardens the part. Feed that's too heavy slows down the machine, creates excessive heat, and causes premature tool failure.
43
When grinding a lathe tool, what wheel do you select for rough and finish grinding carbides?
For rough grinding carbides, use an 80-grit silicon carbide (SiC) wheel. Use a 100-grit silicon carbide wheel for finish grinding carbides.
44
When grinding lathe cutting tools how should you dress the grinding wheel and why?
Dress the silicon carbide wheels with a 1/16"crown to minimize the amount of heat generated during grinding.
45
When grinding lathe cutting tools on a diamond wheel, what grit do you use?
With diamond grinder wheels 100-grit are excellent for finish grinding for carbides for general work. Use a 220-grit diamond wheel if you need a fine finish on the cutter.
46
When grinding carbide lathe cutting tools how much pressure do you use?
The cutting pressures required to remove carbides are 5 to 10 times as great as those required to grind high-speed steel tools.
47
When grinding carbide lathe cutting tools how should you move the bit?
When grinding, move the carbide tool back and forth over the grinding wheel face to keep the heat and friction down.
48
When grinding carbide lathe cutting tools how should you quench the tool?
Don't quench carbide tools that become hot during grinding; allow them to cool gradually. The shock of quenching carbide tools creates small heat cracks and results in rapid tool failure.
49
After grinding a carbide lathe cutting tool why do you hone the edge?
After you grind carbide cutting tools, hone their cutting edges. The purpose of honing is to remove the ragged edge left by the grinding wheel.
50
When honing a lathe carbide cutting tool, when do you hone a chamfer in it?
On carbides used for cutting steel, hone a 45 degree chamfer 0.002" to 0.004" wide on the cutting edge. Carbide tools used for Al, Mg, and plastics don't need it.
51
What is red hardness in high-speed steel?
The ability to retain hardness and strength at high machining temperatures.
52
What does depth hardness enable in high-speed steel tool bits?
The ability to be ground, used, and reground without losing hardness.
53
List the main alloying elements in high-speed steel.
W, Mo, Cr, V, and C.
54
When you select carbides for machining operations, how should you select them?
First, select the group based on the material you’re machining, and then select the grade for the hardness of the material you’re machining.
55
When selecting cemented carbide tools for light finishing cuts, which grade should you select?
Wear-resistant straight carbide with more W.
56
Briefly describe a coated carbide insert.
A cemented carbide insert, known as a substrate, coated with a thin layer of TiC, TiN, or Al2O3.
57
What’s the process of sintering?
Holding materials under pressure at just below their melting temperature until the materials fuse into one solid mass.
58
Why are ceramic tools ineffective in machining Al or Al alloys?
Because they contain Al2O3, which can react with the workpiece and fuse the cutter and the workpiece together
59
What cutting tool material is actually layered onto the base material and forms part of the tool?
CBN.
60
Why can’t you machine Co or nickel with PCD cutting tools?
Because Co and nickel chemically react with the diamond and cause rapid tool wear.
61
What does the side cutting edge do?
The edge that performs the cut
62
What does the nose do?
Connects the side cutting edge to the end cutting edge and produces the finish.
63
What does the end cutting edge do?
Provides clearance for the side cutting edge
64
What does the flank do?
The relieved surfaces below the cutting edges that permit the cutting edges to penetrate the work
65
What does the face do?
The surface for chip formation and determines the shear angle of the chip.
66
How can you identify a right-hand lathe cutting tool? A left-hand lathe cutting tool?
The cutting edge is on the left when viewed from the shank; the cutting edge is on the right when viewed from the shank.
67
What are relief angles and what is their purpose?
The angles formed by the intersection of the cutting edges and the plane perpendicular to the tool shank; allow the cutting tool to penetrate the workpiece.
68
What cutting tool has more cutting edges available, a negative-rake tool or a positive-rake tool?
Negative rake
69
How should you set the nose radius on a cutting tool to keep it from chattering?
Reduce the size of the nose radius.
70
What are the two types of cemented-carbide lathe cutting tools?
(1) Brazed tip. (2) Indexable insert.
71
What are the advantages of a negative rake insert?
They have twice as many cutting edges as positive rake tools, are stronger, and can withstand shock loads.
72
How can you keep long chips from forming when using carbide insert cutting tools?
Use positive-negative rake inserts with a chip breaker.
73
Why are carbide inserts replacing brazed tip inserts in machine operations?
They don’t require grinding, take less time to change, and are less expensive.
74
What occurs if the nose radius on the cutting tool is too large? Too small?
Too large causes chatter; too small causes the point to break down quickly
75
How should you set up carbide tools for machining?
In a tool holder with minimum overhang and exactly on center.
76
What are the effects of too light a feed? Too coarse a feed?
Too light causes work hardening; too heavy slows the machine, generates excessive heat, and causes premature tool failure.
77
How should SiC wheels be dressed? Explain why.
With a 1/16″ crown; minimizes the amount of heat generated during grinding.
78
List two important points to remember when you grind carbide cutting tools.
(1) Move the tool back and forth over the wheel face to keep heat and friction down. (2) Don’t quench hot cutting tools; let them cool gradually.
79
What are the two types of advanced ceramic materials in widespread use?
(1) Ceramic coatings. (2) Refractories.
80
List the most common nonoxide matrices that offer superior structural properties, hardness, and corrosion resistance.
SiC, silicon nitrate, boron carbide, and AIN.
81
Which is identified as the best ceramic for mechanical and wear applications, such as metal processing and cutting tools?
Si3N4.
82
What ceramic displays the highest corrosion resistance of all advanced ceramic materials?
SiC.
83
What ceramic is the most widely used, and is extremely hard and durable?
Al2O3.
84
What is the melting point of Ceramic inserts?
Ceramic inserts have a melting pint of 3,700 F and are capable of withstanding extremely high temperatures.
85
How hot can silicon carbide withstand and retain its strength?
Silicon carbide withstands very high temperatures and retains its strength at temperatures as high as 1,400 C.
86
What are the three classes of lathes?
Toolroom, engine, and turret.
87
What class of lathe is the most common in the Air Force?
Engine lathes
88
What are engine lathes used for?
They're used for general purpose work in support of aircraft and support equipment (SE) maintenance.
89
What are toolroom lathes used for?
Toolroom lathes are more accurate than engine lathes, and have attachments and accessories for a broader range of precision work.
90
What are turret lathes used for?
Turret lathes are used mainly in production work.
91
What determines the size of a lathe?
The size of a lathe is designated by the maximum diameter workpiece that can be swung over the ways, distance between centers, and overall length of the bed.
92
Smaller lathes are sized using?
Inches.
93
Larger lathes are sized using?
Feet.
94
What are the major components of a lathe?
The major components include the bed and ways, headstock, tailstock, carriage, and gearbox.
95
Where is the headstock located on a lathe?
The headstock mounts on the operator's left end of the lathe.
96
Why is a lathe headstock spindle hollow?
the headstock spindle is hollow to allow bar stock and spindle attachments to pass through.
97
There are three different kinds of headstock spindle noses, what are they?
Long tapered, cam-lock, and threaded.
98
What precautions should you take before mounting a chuck or a faceplate on a spindle?
Keep all spindle noses free of nicks and scratches, and carefully clean them before you mount a chuck or faceplate. Also, clean the surfaces of the chucks or faceplates, and keep them free of any nicks, scratches, or dents.
99
What function does the bed and ways serve?
The bed is the base for the lathe. The ways run the full length of the bed, and provide alignment and a bearing surface for the tailstock, carriage, and headstock.
100
How do you protect the ways on a lathe?
To keep a lathe performing accurately, protect it. Don't use the lathe bed as an anvil or a tool shelf. Keep it clean and free of chips, and wipe it off daily with an oiled rag to preserve its polished surface.
101
The tailstock serves three functions what are they?
1. It supports one end of a workpiece when it's turned between centers.
2. It supports long workpieces held in lathe chucks.
3. It holds drills and reamers for machining operations.
102
What does the carriage on a lathe carry?
The carriage carries the cross-slide and compound rest.
103
What does the compound rest on a lathe carry?
The compound rest carries the toolpost and cutting tool.
104
How does the carriage on a lathe move?
Longitudinally on the bed ways by manual or power feed.
105
How does the cross slide on a lathe move?
The cross slide moves perpendicular to the perpendicular to the lathe axis.
106
On a lathe, what mounts to the cross slide?
The compound rest mounts on the cross slide.
107
with the compound rest what direction can you take cuts?
The compound rest permits you to take cuts parallel to, perpendicular to, or at angles to the workpiece axis.
108
When do you lock the carriage to the bed of the lathe?
Use the clamp screw only when performing facing or cutoff operations, since they don't require longitudinal feed.
109
On a lathe what does the lead screw do?
The lead screw drives the carriage when you cut threads on a lathe.
110
When you inspect a lathe what do you check for?
```
Machine for level stance.
Spindle bearings for play.
Clutches for slippage.
Gibs for wear and looseness
Cross feed and lead screws for play and backlash.
Gearing for lost motion and wear.
Machine for lubrication.
```
111
How often should you change your lathes headstock oil?
Every six months.
112
How are lathe chucks identified and what are they?
Lathe chucks are identified by type which are universal, independent, combination, and collet chucks.
113
Describe Universal chucks.
On the universal chuck all of the jaws open and close simultaneously with the chuck key. You can quickly change workpieces.
114
Describe Independent chucks.
Independent chucks have jaws that move independently of each other, giving them a wide range of uses.
115
Which chuck has the greatest holding power of any chuck?
The four-jaw independent chuck has the greatest holding power of any chuck because you can tighten each chuck jaw independently.
116
What are the methods for aligning a workpiece in an independent chuck?
You can approximate how true you have the workpiece set by aligning the chuck jaws with a series of concentric circles machined on the chuckface.
You can get closer alignment by marking the workpiece with chalk or a marker.
For closer accuracy, align the work using a dial indicator.
117
Describe the combination chuck.
Combination chucks have features of both universal and independent chucks. The jaws can be adjusted independently or all together.
You can use the combination chuck for chucking duplicate pieces of irregularly shaped work.
118
Should you thread or part in a lathe collet? Why?
No, Threading and parting in collets can cause them to spring out of shape, or the workpieces can slip.
119
How do you select a collet for lathe work?
Don't select a collet more than 0.005" larger than the workpiece, and never select a collet smaller than the workpece.
120
What are the three most common type of lathe collets are there?
1. Draw bar
2. Spindle-nose
3. Rubber-flex
121
What type of lathe collet is the weakest?
Rubber-flex collets are the weakest collets, so don't thread, part, or take heavy cuts while using them.
122
What should you do before mounting a workpiece on a faceplate?
Before you mount a workpiece, check the faceplate with a dial indicator.
123
When taking a truing cut on a faceplate how do you set the spindle speed?
Set the spindle speed based on the outside diameter of the faceplate, and set the cutting speed at about 50 fpm.
124
When taking a truing cut on a faceplate, how should the compound rest be set?
Set the compound rest parallel to the lathe axis and take the depth of cut with the compound rest dial.
125
When mounting work on the faceplate, what should you do if you will take heavy cuts?
If you're going to take deep roughing cuts on a workpiece mounted on a faceplate, bolt a block or scrap material against one side of the workpiece to act as a driver to keep the workpiece form shifting while under cutting pressure.
126
When using lathe dogs, how can you protect finished surfaces?
Place shim stock between the lathe dog and workpiece to protect any finished surfaces.
127
How are driveplates different than faceplates?
A driveplate is similar to a faceplate and mounts on a lathe the same way. It has from one to four radial slots machined in it, but it doesn't have T-slots, so you can't mount work directly on it.
128
What is the advantage of turning work between centers?
The main advantage of machining work between centers is you can remove the work from the lathe and replace it later without affecting the trueness of the tuned surface in relation to the center holes.
129
How can you check the alignment of tailstock?
Cricket mark, visual, dial indicator, and cut-and-try.
130
What is the included angle on a male type center?
The male center has a conical point with a 40 degree included angle.
131
How do you repair a male tailstock center?
Use a toolpost grinder with the compound rest swiveled 30 degrees from the axis of the center; this gives you the included angle of 40 degrees. Ensure the spindle and grinding wheel are turning in the same direction at the point of contact. Take light cuts to keep from burning the center.
132
When drilling center holes, how do you determine the size of the hole?
Work diameter - The greater the diameter, the larger the center hole should be.
Material hardness - Softer materials need larger center holes.
Machining with heavy cuts or knurling need larger center holes.
133
When using a mandrel where should you use lubricant?
use a thin film lubricant film on the shaft and mandrel to keep them from galling as you press them together.
134
Describe the solid mandrel.
The solid lathe mandrel is hardened, tampered, and accurately ground with a 0.006" taper per foot.
Solid mandrels come in fractional sizes, with the size of the mandrel always marked on the large end to distinguish it from the small end.
On mandrels that are up to 1" in diameter, the small end of the mandrel is usually 0.0005" smaller than the standard size. On mandrels over 1", the small end is ground 0.001" undersize.
135
Describe eccentric mandrels.
The eccentric mandrel is almost identical to the solid mandrel. The difference is an eccentric mandrel has a series of center holes at each end.
If you mount them using the offset center holes you can turn the outer diameter of the work eccentric to its bore.
136
Describe nut mandrels.
Nut mandrels hold work when you machine surfaces concentric to threaded holes. You screw the work on the mandrel, and the shoulder acts as a stop and helps drive the work.
137
Describe gang mandrels.
Gang mandrels hold several workpieces so you can machine them to the same outer diameter.
138
describe tapered plug mandrels?
A tapered plug mandrel is used to hold work that has tapered holes.
139
What’s the difference between a toolroom lathe and an engine lathe?
An engine lathe is a general-purpose machine; a toolroom lathe is an accurate lathe designed for precision work.
140
What kind of lathe is used mainly for production work?
Turret lathe
141
How is the size of a lathe designated?
By the maximum diameter workpiece that can be swung over the ways, distance between centers, and overall length of the bed
142
Which lathe headstock design permits you to mount driveplates with cam studs?
Cam-lock spindle nose.
143
What is the purpose of the ways on a lathe?
To provide alignment and a bearing surface for the tailstock, carriage, and headstock.
144
What lathe component supports long workpieces for production?
The tailstock.
145
How does a lathe carriage move?
Longitudinally on the bed ways by manual or power feed.
146
At what angle to the axis of the lathe does the cross slide move?
Perpendicular
147
What lathe component transmits power to the apron to drive the feeds?
The feed rod.
148
What type of threads are found on the lead screw of a lathe?
Acme.
149
To be sure a lathe remains in good condition, what should be included in the periodic checks?
Machine for level stance; spindle bearing for play; clutches for slippage; gibs for wear and looseness; cross feed and lead screw for play and backlash; gearing for lost motion and wear; and machine for lubrication.
150
What do gibs do? How do you adjust them?
Gibs take up wear between bearing surfaces; by loosening the lock screw, tightening the gib screw until you have smooth, snug fit, and then tightening the lock screw.
151
What condition can be checked by engaging the half nut and moving the carriage back and forth by hand?
End play in the lead screw.
152
How often should you change the oil in a lathe headstock?
Every six months
153
Which lathe chuck should you use to hold hexagonal stock on a lathe when you don’t need extreme accuracy?
Universal.
154
Which chuck is best suited for aligning off-centered workpieces?
Independent.
155
How should you adjust independent chuck jaws for indicating?
Adjust only two opposite jaws at a time to zero the high and low spots, and then adjust the remaining two opposite jaws.
156
Which chuck eliminates the need for truing?
Collet.
157
What is the maximum oversize steel collet you should select for a workpiece?
0.005
158
Which type of collet chuck has the weakest holding power?
Rubber-flex
159
When you’re truing a faceplate, what should you check before you take a light facing cut?
The spindle nose and the hole in the faceplate.
160
How deep should clean-up cuts be when you true a faceplate?
Shallow cuts 0.001 to 0.003″ deep.
161
What precaution should you take when you are taking deep roughing cuts on a workpiece mounted on a faceplate?
Bolt a piece of scrap material against the following side of the workpiece to act as a driver.
162
What precaution should you take when you’re machining a heavy workpiece off center?
Add a counterbalance.
163
What is the purpose of the slots in a driveplate?
They are used to drive a lathe dog.
164
How can you keep from damaging finished workpieces when you use lathe dogs?
Place shim stock between the lathe dog and workpiece.
165
What are the tailstock and headstock centers called?
Dead center; live center.
166
What alignment methods are used for approximation only?
Cricket mark and visual.
167
Which lathe center should you use for workpieces with pointed ends?
Female.
168
When facing work held between centers, which type of centers should you use?
Half.
169
What effect does the hardness of material have on the size of the center hole in a piece of stock?
The softer the material, the larger the center hole should be.
170
When drilling center holes, how does the size of holes subjected to heavy pressure differ from those subjected to light pressure?
Those subjected to heavy pressure are larger.
171
How is a part mounted on an eccentric mandrel?
By pressing it in with an arbor press.
172
How much TPF is ground on a solid mandrel?
0.006″.
173
Why is the size of a solid mandrel always stamped on the large end?
To distinguish it from the small end.
174
What is the diameter of the small end of a 1.250″ mandrel?
1.249″.
175
Which mandrel should you use to machine the surface of a part that has a threaded hole?
Nut.
176
What is the formula for cutting speed?
rpm = CFS X 4 / Dia.
177
What is the recommend CFS for low-C steel?
80-100.
178
What is the recommend CFS for medium-C steel?
40-80.
179
What is the recommend CFS for high-C steel?
50-40.
180
What is the recommend CFS for steel forgings?
30-40.
181
What is the recommend CFS for stainless steel?
100-150.
182
What is the recommend CFS for soft cast iron?
70-100.
183
What is the recommend CFS for hard drilled cast iron?
80-90.
184
What is the recommend CFS for malleable iron?
80-90.
185
What is the recommend CFS for ordinary brass or bronze?
200-300.
186
What is the recommend CFS for high-tensile bronze?
70-150.
187
What is the recommend CFS for monel?
40-150.
188
What is the recommend CFS for Al alloys?
200-300.
189
What is the recommend CFS for Mg alloys?
250-400.
190
What is the recommend CFS for bakelite?
100-150.
191
What is the recommend CFS for wood?
300-400.
192
What is the general rule for taking roughing cuts?
A general rule is to take rouging cuts or 0.250" on workpieces over 0.750".
193
After taking roughing cuts how much material should be left?
After you've completed "roughing," you should have 0.010 to 0.020" left for finishing.
194
How do you pick up the cut after switching tools form roughing to finishing?
You pick up the cut by placing a piece of paper between the tool and the rotating workpiece, and feeding the tool toward the workpiece until the paper drags.
195
When straight turning, where do set the compound rest and why?
Set the compound rest 30 degrees to the right of parallel with the cross slide. With this setup, you have less chance of running the toolpost and compound rest into the lathe chuck during operation.
196
During facing operations, how far can the workpiece extend out of the lathe chuck?
Allow only 1 1/2 times the workpiece diameter to extend out of the lathe chuck for facing.
197
How can you set a lathe cutting tool to center height?
Align the tool point with the point of a center mounted in the tailstock.
Align the tool with the center regerence line machined on the tailstock spindle.
align the tool by setting the point with a surface gage set at center height.
take trial cuts and adjust the tool point to center after making the cuts.
198
Describe the parting tool geometry?
They are ground so the cutting edge is the widest part of the tool and both sides of the tool have a 1 to 2 degree flank relief. The end relief should be 10 degress for harder materials and 15 degrees for softer materials.
199
What type of chuck do you use for parting on a lathe?
Use a four-jaw chuck and make the cut as close as possible to the lathe chuck to keep the part from springing.
200
What feed should you use for parting?
Use a feed rate of 0.002" per revolution and ensure there's a continual , thin chip from the cut.
201
What is step parting?
In step parting, you feed the tool into the work a short distance. then, you withdraw the tool from the groove, move the carriage slightly to the scrapside, and feed the tool in again. This procedure leaves only one side of the tool cutting in the groove and prevents binding.
202
What two things do you need to know to calculate the required spindle rpm for a turning operation?
The recommended CFS and diameter of the workpiece.
203
What spindle rpm do you need for turning a 4″-diameter C steel pulley with a CFS of 80? Work the problem out using the correct formula.
rpm = CS X 4 / Dia = 80 X 4 / 4 = 320 / 4 = 80.
204
What’s the recommended feed rate for rough turning medium C steel?
40–80 CFS.
205
During a roughing operation on a lathe, how much of a depth of cut should you take?
As heavy as workpiece setup, tool setup, and machine rigidity allow.
206
After you’ve completed the roughing operation, how much material should you have left for finishing?
Between 0.010″ and 0.020″.
207
When you pick up the cut for a finishing operation, why should you only cut about ¼″ of the length before you take a measurement?
To see if the cut is within tolerance.
208
How should the compound rest be set when straight turning? Why?
30° to the right of parallel with the cross slide; this setup has less chance of running the toolpost and compound rest into the chuck.
209
How much material should you permit to extend beyond the lathe chuck for facing?
1½ times the workpiece diameter.
210
For a facing operation, how should you set the cutting tool height?
At center height.
211
List the methods you can use to face a workpiece to length.
Layout the workpiece and face until you split the layout line; take a cut and measure the depth after every cut; measure to length with a micrometer or caliper, and take depths of cut with the compound rest; and set the depth of cut with the lathe micrometer stop.
212
Which machined shoulder is stronger, a turned square shoulder or a fillet? Why?
Fillet; there is better transfer of stress from a fillet than a square shoulder.
213
Why would you turn an angular shoulder on a workpiece?
To give strength to corners, eliminate sharp corners, and improve workpiece appearance.
214
List the methods you can use to turn a chamfered corner.
Turn the cutter to the angle you want to machine; swivel the compound rest to the angle you want to machine; or use a square nose cutter.
215
How can you “break” a square corner?
By filing a small amount of material to remove the burr.
216
What’s the purpose of machining undercuts in workpieces?
To reduce shaft diameters and weights, and provide runout clearances for threading, milling, and grinding operations.
217
How can you check a groove tool to ensure it cuts the correct size radius?
Use a radius gage.
218
How can you keep a workpiece from springing as you part it?
Make the cut as close to the lathe chuck as possible
219
If you were parting a .500″ workpiece to length using a .187″ parting tool, how would you set the micrometer stop?
.687.
220
Why should you lock the lathe carriage during a parting operation?
To keep it from moving while you take a cut.
221
Describe the template and pointer method of cutting a radius.
When you use a template and pointer, you lay out the full-scale form of the work on a piece of thin sheet metal. Then, you clamp the template to the lathe bed and attach a pointer to the lathe cross slide and hand manipulate the cross slide and carriage.
222
Describe a lathe radius attachment
The radius attachment is a swivel type tool that is used to cut convex and concave radius's.
To cut a convex radius, set the yoke so the cutting tool swivels behind the pivot point.
To cut a concave radius, set the yoke so the cutting tool swivels ahead of the pivot point.
223
How can you set the compound rest more accurately?
You can set the compound rest more accurately by using a Vernier bevel protractor and dial test indicator attached to the compound rest slide.
224
What is the spindle speed for filing metals?
Four to five times faster than the rough turning speed.
225
On polishing how do you produce a bright surface?
Polish the work while it is dry.
226
On polishing how do you produce a dull satin surface?
Apply oil as you polish.
227
What speed should the spindle be when polishing?
5,000 surface feet per minute, or as fast as it will go.
228
Describe the hand manipulation technique for turning a radius.
By moving the cutting tool on an irregular path as you simultaneously move the carriage and cross slide.
229
How can you justify the time spent grinding a form tool?
When you have a multiple of identical forms to turn.
230
If you are using a form tool and find that it chatters, what’s the probable cause?
The speed is too high.
231
When you turn a radius with the compound rest, how do you set the rest for concave radii or for convex radii?
Position the cutting tool in front of the pivot point; position the cutting tool behind the pivot point.
232
For what type of taper is the compound rest best suited?
Steep and short.
233
Describe the procedures for calculating the angle of the compound rest when you have the dimensions of the taper, but you don’t have the TPI.
Use the formula TPI = LD - SD / LT to calculate TPI.
Use the TPI to solve the formula TAN< = TPI / 2 to determine the taper angle.
234
What should you be especially concerned with when turning an internal taper?
The back of the toolbit rubbing the taper surface as you back the tool off the cut to bring it out of the hole.
235
Describe the correct way to hold a file when filing work in a lathe. An abrasive strip for polishing in a lathe.
The file handle in your left hand with the tip at about a 10° angle toward the tailstock and the file tip in your right hand; with the ends separated.
236
Explain how to calculate the TO when you have the TPI and LW.
Use the formula: TO = TPI / 2 X LW.
237
How is the TPI affected as the LW increases if the TO remains constant?
It decreases.
238
Explain the procedure for measuring the amount of TO when using the cross slide graduated collar method.
Bring the side of the toolpost into light contact with the tailstock spindle; move the toolpost away from the tailstock spindle with the cross slide to eliminate backlash; set the cross slide graduated collar to zero; move the toolpost toward the tailstock spindle with the compound rest until you feel a slight drag on a strip of paper between the tailstock spindle and toolpost when you pull on the paper; move the toolpost away from the tailstock spindle with the cross slide handwheel and read the graduated collar to get the required offset; then, offset the tailstock toward the toolpost until you feel a slight drag on a strip of paper between the tailstock spindle and toolpost when you pull on the paper.
239
List the disadvantages of machining a taper with the TO method.
Slight variations in workpiece lengths or depths of center holes cause variations in the amount of taper when you’re trying to machine duplicate workpieces; the center holes don’t uniformly seat on the lathe centers, which can cause the centers to score; you must realign the centers after the operation so you can straight turn; you can only turn external tapers, since this method requires you to turn the workpiece between centers; and the TO and LW limit the amount of taper you can turn (the range of offset of the tailstock varies from approximately ½″ on small lathes to 1½″ on larger lathes).
240
What advantages does the taper attachment have over the offset tailstock method of turning tapers?
It can machine internal and external tapers; it has a greater range of travel than the compound rest; you don’t need to offset and realign the lathe; there is less wear on the centers and center holes when using the taper attachment; and you can machine duplicate tapers on workpieces of different lengths without changing the taper setting.
241
Name what the parts of the taper attachment does, carriage bracket.
Supports the taper attachment.
242
Name what the parts of the taper attachment does, drawbar.
Connects the cross slide to the guide block.
Relieves the strain on the cross slide screw.
243
Name what the parts of the taper attachment does, guide block.
Causes the cross slide to move in relation to required angle.
244
Name what the parts of the taper attachment does, guide bar.
Swivels to produce required taper.
| Acts as a guide for the guide block.
245
How can you eliminate backlash when you are machining a taper with the small end near the headstock?
As you position the tool for another cut, make the last movement of the cross slide away from you.
246
You must machine a taper with a 0.0625 TPI. You decide to use the TPF graduation on the taper attachment guide bar. Show the formula you used to arrive at this conclusion.
TPF = TPI X 12 = 0.0625 X 12 = 0.750" or 3/4".
247
When drill bits are larger than 5/8" you mount them directly in the _______?
Tailstock spindle.
248
At what size does a drill bit need to be before you need to attach a lathe dog to it.
If you're performing a heavy drilling operation with a drill bit larger than 1 1/2" in diameter, attach a lathe dog to the neck of the drill bit to keep it from turning in the tailstock.
249
What are the methods of regulating a drill depth?
You can use the graduations on the tailstock spindle.
You can also scribe a line on the drill or tailstock.
250
When you hand ream how should you prepare the hole?
Rough-drill the hole approximately 1/32" undersize.
Bore the hole to within 0.003 to 0.005"
Ream the hole.
251
When you machine ream how should you prepare the hole?
Rough drill or bore the hole to within 0.010 to 0.015" of final size.
252
What should the spindle speed be set at for machine reaming?
Set the spindle speed for machine reaming to half the drilling speed for a hole of the same diameter.
253
When boring, what size should the the hole be rough drilled to?
You should make the drilled hole about 1/32" smaller in diameter then the size of the finished bore.
254
How do you set up the tool for boring?
For straight boring 5 degress above center, for taper boring, set it on center.
255
What are the angles of a boring tool?
The angles ground on boring tools vary based on workpiece materials. Boring tools with 10° side relief and back-rake angles (fig. 3–9A) and a 15° side-rake angle (fig. 3–9B) are commonly used for boring steel. The end relief angles on boring bars vary with the hole diameters. When the hole diameter decreases, you must increase the end relief to keep the tool from bottoming out in the workpiece. Grind the end relief angle so the heel of the tool does not rub the surface of the hole. Figure 3–9C shows insufficient end relief. You can grind the end of a boring tool (fig. 3–10A) for boring to a shoulder. Grind it with a 20° entrance angle (fig. 3–10B) for boring completely through a hole.
256
What are some other names for Recessing?
Recessing, sometimes called channeling or chambering, is the process of machining a groove.
257
What methods can you use to mount drills in a lathe?
In a drill chuck or tailstock spindle, or floated on dead center.
258
How can you mount a taper shank drill in a tailstock if the tapers between the drill and tailstock are different?
By using a socket reducer.
259
When you rough-drill a hole for hand reaming, how much material should you leave? For machine reaming?
1/32″; 0.010 to 0.015″.
260
What spindle speed should you use for machine reaming?
Half the drilling speed for a hole of the same diameter.
261
What are some advantages of boring?
Produces round and concentric holes; you can bore true holes for reaming; you can finish bore holes to any size and leave allowance for reaming; you can produce odd-sized holes.
262
How does the boring speed compare to the turning speed on material of the same diameter as the hole?
They are the same.
263
What governs the amount of end relief ground on a boring tool?
The diameter of the hole.
264
What is the cause of a bell-mouthed hole? How do you correct it?
Spring in the boring bar, a dull tool, or too heavy a cut; by occasionally feeding the tool out of the hole at the same setting you used to feed it into the hole, sharpening the tool, or reducing feed or depth of cut.
265
How do you check internal tapers?
With a taper plug gage, the mating part, or a protractor.
266
What’s the purpose of recessing a workpiece?
Provides room for tool runout, seats for snaprings and O-rings, and lubrication channels.
267
Parts of threading, define Allowance.
The intentional difference between the maximum limits of mating parts. It is the minimum clearance between freely fitting parts or the maximum interference between parts having an interference fit.
268
Parts of threading, define Crest.
The top surface joining the two sides, or flanks, of the thread.
269
Parts of threading, define Crest clearance.
The distance between the crest of a thread and the root of its mating thread.
270
Parts of threading, define Fit.
The relationship between two mating parts based on the amount of clearance or interference between them when they’re assembled.
271
Parts of threading, define Flank.
The side of a thread surface connecting crest and roots.
272
Parts of threading, define Lead.
The distance a screw thread advances in one turn. On a single-thread screw, the pitch and the lead are equal; on a double-thread screw, the lead is twice the pitch; on a triple-thread screw, the lead is three times the pitch; and so forth.
273
Parts of threading, define Lead angle.
The angle made by the helix of the thread at the pitch diameter.
274
Parts of threading, define Left-hand thread.
A thread with the grooves cut so a machine screw or a bolt advances in a counterclockwise direction, when viewed from the head end.
275
Parts of threading, define Major diameter.
The largest diameter of a straight screw thread (applies to internal and external threads) measured at the crest of the thread.
276
Parts of threading, define Minor diameter.
The smallest diameter of a straight screw thread (applies to internal and external threads) measured at the root of the thread.
277
Parts of threading, define Nominal size
Describes the size of the thread for identification. For example, the nominal size of a ½”, 20- taper/thread per inch (TPI) screw thread is ½”, but its actual major diameter ranges from 0.4987 to 0.4906”.
278
Parts of threading, define Pitch
The distance from a point on one thread profile to a point on the next thread, measured on a line parallel to the axis. The pitch is equal to one divided by the number of TPI as shown in the following formula:
Pitch = 1 /TPI
279
Parts of threading, define Pitch diameter
The diameter of an imaginary cylinder concentric with the thread axis. Its periphery passes through the thread profile where the width of the thread and the thread groove are equal. It’s the diameter you measure to machine a thread to size. A change in pitch diameter changes the fit between the thread you’re machining and it’s mating part.
280
Parts of threading, define Right-hand thread
A thread with the grooves cut so a machine screw or a bolt advances in a clockwise direction, when viewed from the head end
281
Parts of threading, define Root
The bottom surface joining the two adjacent sides or flanks of the thread.
282
Parts of threading, define Thread designation
A thread is designated according to the nominal size, number of TPI, series symbol, and class symbol. For example, the designation ¼–20 UNC–3A means: 1/4 = nominal threads diameter. 20 = number of TPI. UNC = series (this is unified national coarse, a type of the American Standard Unified thread series). 3 = class. A = external thread. NOTE: The designation for a left-hand thread would be 1/4–20 UNC–3A–LH.
283
Parts of threading, define TPI
The number of TPI measured parallel to the thread axis. This term is used in conjunction with the outside diameter (OD) to designate the size of the thread.
284
Parts of threading, define thread.
The helical groove cut on the outside of a shaft or the inside of a hole.
285
Parts of threading, define Tolerance.
The difference between the maximum and minimum limits of size; the total permissible variation in size.
286
Name and define all 4 Thread series.
UNC—Unified National Coarse Series.
UNF—Unified National Fine Series.
UNEF—Unified National Extra-Fine Series.
UNS—Unified National Special Series.
287
What is the thread class 1A and 1B?
These classes are intended for ordnance work and applications where quick and easy assembly is necessary. They have a liberal allowance to permit the parts to be assembled easily, even with dirty or slightly damaged threads. The tolerances specified for the 1A (or external) threads are not the same as those specified for the 1B (or internal) threads.
288
What is the thread class 2A and 2B?
These classes are most commonly used for general applications including bolts, nuts, and screws. This series provides minimum clearance between mating threads to permit the threads to assemble without being excessively loose, but also without binding or seizing.
289
What is the thread class 3A and 3B?
These classes have the closest tolerances. The maximum diameter of a Class 3A thread is equal to the minimum diameter of a Class 3B thread
290
What does the A thread designate?
External thread.
291
What does the B thread designate?
Internal thread.
292
With metric threads how can you know if the thread is external or internal?
At the end of the thread designation, is the class of fit, if this ends in an upper-case letter it is an internal thread. If it ends in a lower-case it is external.
293
Name what the metric thread 5H means.
Internal threads close fit.
294
Name what the metric thread 6H means.
Internal threads medium fit.
295
Name what the metric thread 7H means.
Internal threads free fit.
296
Name what the metric thread 4g means.
External threads close fit.
297
Name what the metric thread 6g means.
External threads medium fit.
298
Name what the metric thread 8g means.
External threads free fit.
299
In metric threads M10 x 1.5, what does the 10 mean?
The nominal size.
300
In metric threads M10 x 1.5, what does the 1.5 mean?
The thread pitch.
301
What is the formula for determining the best wire size?
0.57735/TPI
302
What is the formula for determining the smallest wire size?
0.56/TPI
303
What is the formula for determining the biggest wire size?
0.90/TPI
304
Formula for determining measurement after wire use?
M=MD-1.5155/T+(3xWD).
305
Cutting even number of threads?
Engage at any graduation 1, 1 1/2 2, 1/2 3, 3 1/2, 4, 4 1/2.
306
ODD number of threads?
Engage at any main division 1, 2, 3, 4.
307
Fractional number of threads?
Engage at every other main division. 1,3 and 2,4.
308
When cutting internal threads where do you position the compound rest?
29 to 30 degrees to the left of parallel. If this will hit the work or chuck 180 degrees from normal.
309
How do you cut left hand threads?
The main exception is, when you cut left-hand threads, you cut toward the tailstock instead of away from it. Also, you swivel the compound rest to the left (instead of to the right) to cut external, left-hand threads, and to the right (instead of to the left) to cut internal, left-hand threads.
310
What is the lead angle of a thread?
The angle made by the helix of the thread at the pitch diameter.
311
What’s the difference between pitch and pitch diameter?
Pitch is the distance from a point on one thread profile to a point on the next thread measured parallel to the axis; pitch diameter is the diameter of an imaginary cylinder concentric with the thread axis.
312
What does each position in thread designation ¼–28 UNF–3B mean?
¼ = nominal diameter. 28 = number of TPI. UNF = Unified fine. 3 = thread class (lowest tolerance of the three classes). B = internal thread.
313
In the thread designation M9 × 1.25–5H, what does 5H mean?
Close fit internal thread
314
Describe the thread gage and thread micrometer methods of measuring threads.
Threaded plug gage is one of the most exact methods of checking internal threads; thread micrometers are highly accurate thread measuring tools that measure threads at their pitch diameters.
315
For a ¼–20–UNC thread, what should the pitch diameter measurement over the wires be if the diameter of the wires is 0.029″? Show all calculations.
M=0.250-1.5155/20+(3x0.029=0.250-0.07577+0.087=0.2612".
316
What is the included angle of a Unified thread?
60°.
317
What two type treading tools should you grind?
One for roughing cuts; another for finishing cuts.
318
How much back-rake angle should a rough threading tool have?
0°.
319
What does the side relief angle of a thread depend on?
The helix angle of the thread.
320
How do you check the form of a threading tool?
With a 60° center gage.
321
When you cut threads on a lathe, how far does the tool move per revolution of the workpiece?
A distance equal to the lead of the thread.
322
What three conditions must be met before machining threads on a lathe?
(1) Proper work preparation. (2) Correct tool setup.
| (3) Proper lathe gearing.
323
What size runout groove should you machine on a workpiece before cutting threads?
The groove should be slightly wider than the thread pitch, and depth should be equal to or slightly greater than the thread depth.
324
At what height should you set the point of the threading tool in relation to the work?
At center height.
325
What’s the spindle rpm for threading?
Slower than regular turning speeds for the type of metal being machined.
326
What are some of the differences between external and internal threading on a lathe?
Internal threading has cutter clearance restrictions and it requires you to mount the threading in a boring bar.
327
How do you set the compound rest for internal threading?
The normal position is 29° to 30° to the left of the perpendicular position; but if clearance between the compound rest and work occur, position it 180° from normal position.
328
Why should you take lighter cuts during internal threading operations?
Because the cutter extends farther out of the tool post.
329
What is the purpose of left-hand threads?
For use in applications where right-hand threads could loosen during operation.
330
What’s the major difference between machining right-hand threads and left-hand threads?
When you machine left-hand threads, you cut away from the headstock instead of toward the headstock.
331
How do you prepare the workpiece for machining left-hand threads?
Machine an undercut at the starting point (make it at least as wide as and slightly deeper than the single thread depth) and chamfer the side nearest the start.
332
Describe multiple threads. Why are they used?
Two or more threads that run parallel to each other around a surface; where parts must assemble quickly without loss of strength; and where a nut and shaft must tighten quickly.
333
What’s the quickest and easiest method of cutting multiple threads?
Use the thread-chasing dial.
334
If you want to machine a double-lead thread having 16 TPI, at how many TPI should you gear the lathe to get the correct TPI?
8 TPI.
335
Which method of cutting multiple threads is especially adapted to cutting Acme and square threads?
The compound rest multiple thread cutting method.
336
What feature do American Standard NPTs have in common with Unified threads?
60° included angles.
337
How do American Standard NPTs differ from Unified threads?
NPTs are machined on a taper of ¾″ per foot.
338
How should you prepare a hole for an internal taper pipe threading operation?
Straight bore it to a diameter equal to, or slightly larger than, the minor diameter of the small end of the mating thread.
339
How do you position the cutting tool for machining taper pipe threads?
With the center gage aligned with the straight portion of the pipe, not with the taper.
340
Describe an Acme thread.
The thread depth is equal to one-half the pitch plus clearance allowance, and the sides form an included angle of 29°.
341
How do you prepare and set up a cutting tool to cut an Acme thread on the lathe?
Grind the tool to fit the Acme thread gage and to fit a thread one pitch size smaller than the thread to be cut. Ensure it has 3 to 6° side clearance, and a 0° side and back rake; use the Acme thread gage to square the tool with the workpiece and set the compound rest parallel to the ways.
342
Describe a square thread.
The thread sides are parallel and the depth is equal to the width of the space between the teeth on external threads.
343
What’s the difference between a threading tool designed for cutting external square threads and a cutting tool designed for cutting internal square threads?
The width is slightly more than ½P; the width is slightly less than ½P.
344
How do you position the compound rest for machining square threads and how do you feed the tool bit into the workpiece?
Parallel to the ways; perpendicular to the work.
345
What two change gears do you need to machine metric threads on a lathe? Where do you mount the gears?
(1) 50-tooth gear on the spindle. (2) 127-tooth gear on the lead screw.
346
What’s the major difference between machining metric threads and Unified Threads?
At the end of each cut, back out the cutting tool and stop the machine, but never disengage the split nut.
347
What is the recommended rpm range for tapping by power?
10 to 30.
348
How do you keep a tap from turning when you are tapping threads by power in the lathe?
By resting a tap wrench on the compound rest.
349
What’s the tap size limitation for tapping by power versus hand?
Don’t power tap with taps under ½″ in diameter.
350
What is the procedure for cutting a thread with a geometric die?
Insert the chasers into the correct slots; set the rough cut and set the finish cut; cut the threads with the rough cut setting; and reset for the finish cut and complete the cut.
351
For what purpose is knurling used?
To make impressions into the work surface for decoration, provide a gripping surface, and increase diameter.
352
Name the patterns and pitches available on knurling tools.
Diamond and straight; fine, medium, and coarse.
353
What’s the procedure to follow if the knurling rollers double track at the start of a knurling operation?
Back the knurling tool away with the cross slide, reposition it, and start again in a new spot.
354
What’s the procedure for starting a knurl between layout lines?
Set up the work, lathe, and knurling tool as usual; swing the compound rest to the right 5° to reduce the starting pressure; position the knurling tool slightly to the left of the right-hand layout line and start the knurl by forcing the corner of the roller into the work surface; move the carriage by hand and, if the knurl is tracking properly, extend the knurl to the right-hand layout line; move the knurling tool clear of the work and position it parallel to the work surface by swinging the compound rest back to the left 5°; and finish knurling the workpiece by using the same technique as ordinary knurling.
355
What important considerations should you remember when knurling?
Don’t allow the workpiece to rotate if the knurling tool is touching it and the carriage travel has stopped because rings will form on the workpiece; don’t stop the workpiece without relieving the knurling tool pressure because the pressure may distort or spring the work; keep the knurling tool and work well oiled throughout the operation; check the tailstock center frequently because the pressure of the knurling operation may cause the center to loosen slightly; and always ensure the setup is rigid so you don’t damage the chuck or ruin the workpiece.
356
How do you set a tool post grinder at center height?
Align the centering holes in the grinding wheel spindle with the headstock center.
357
How are grinding wheels for internal grinding mounted?
On tapered shafts called quills.
358
How do you set up a diamond dresser for dressing and truing a tool post grinder?
Mount it in a holder clamped to the driveplate, and then set the point of the diamond at the center height and angle it 10 to 15° in the direction of wheel rotation.
359
For external and internal grinding with a tool post grinder, how should the grinding wheel and workpiece rotate?
For external cylindrical grinding, set the workpiece and the grinding wheel so they rotate in the opposite direction at the point of contact; for internal grinding, the wheel and the workpiece run in the same direction at the point of contact.
360
How are center rests used?
Prevent slender stock from springing; provide auxiliary support to permit heavier cuts; and provide support for drilling, boring, or internal work.
361
What should you do to protect the work surface when using the center rest on ground work?
Use copper shims between the work and center rest jaws.
362
What’s the difference between a follower rest and center rest?
The follower rest has only two jaws and is mounted to the carriage; the center rest has three jaws and is mounted to the ways.
363
How close can you set a cutting tool when you use a micrometer stop?
Within 0.001″ tolerance.
364
What’s the purpose of the dovetails on a quick-change tool post?
To provide a positive hold and accurate setting for multiple tool holders.
365
What is the repeat accuracy of the quick-change tool post?
0.0001″.
366
How do you adjust tool bits to center height when you are using a multiple tool holder?
By using shims
367
What’s the standard spindle taper for milling machine arbors?
3½″ per foot.
368
The large end of a milling machine spindle taper is 2¾″. What is the arbor’s taper number?
50.
369
What does arbor designation 4–1–A–12 mean?
#40 taper, 1″ shaft, pilot style arbor, and 12″ usable shaft length.
370
What does the code 5–2–C–1 on a stub arbor mean?
#50 taper, 2″ diameter mount hole in end mill, style C arbor, and 1″ shaft length.
371
What’s the disadvantage of cemented carbides?
They’re brittle and can fracture in an interrupted cut.
372
What feature of deposit-coated high-speed steel cutters helps prolong tool life?
The deposited coating keeps the cutter from chemically reacting with the workpiece material.
373
What’s the land on a milling cutter?
The narrow clearance behind the cutting edge on each tooth.
374
What features on a milling cutter keep the cutting edges from rubbing the workpiece?
Relief angles.
375
Why should you select a cutter with a slightly negative rake angle if you’re milling soft materials?
To keep the cutter from digging in.
376
Give the advantage of using milling cutters with helical teeth.
They reduce shock by starting the cut at one end and following through to the finish.
377
How can you convert a straight tooth side milling cutter to a form cutter?
By grinding the teeth to the required outline.
378
Which type of milling cutter has a width of less than 3/16″?
Metal slitting saw.
379
Which cutters are made in various thicknesses to correspond with American Standard gage wire numbers?
Screw slotting.
380
In performing a milling operation where you must cut dovetail ways, what cutter should you select
Angular.
381
Which cutter features the ability to replace the cutter teeth if they wear out?
Indexable insert.
382
What are the two types of milling machines?
(1) Vertical spindle. (2) Horizontal spindle.
383
How are milling machines sized?
Longitudinal (left to right) table travel in inches.
384
What should you do before you permanently install a milling machine around other shop machinery?
Study the floor plan and allow plenty of room around the dimensions of the machine.
385
How can you keep rust off the exposed metal surfaces of a milling machine?
By keeping a light film of clean oil on them.
386
What happens if you adjust the gibs of a milling machine too tightly? Too loosely?
The dovetail ways will be scored; the machine will chatter and vibrate.
387
At which end of the table is the table feed screw adjusting collar?
The right-hand.
388
What must you remove to adjust loose cross feed screw bearings?
The cross feed handwheel, powerfeed lever, and graduated dial.
389
What determines the relief angles on the periphery of an end mill?
The diameter of the end mill and the material it’s milling.
390
What’s a disadvantage of using end mills with four or more flutes?
Slower chip removal rates.
391
How can you set up an end mill to reduce the possibility of deflection?
Set up as close to the spindle nose as possible.
392
Which end mill should you use for plunge cutting?
Two-flute.
393
You have a keyseat milling operation that requires a #808 Woodruff key. What’s the size based on the code?
¼″ width, 1″ diameter.
394
What items are included in the code for a taper adapter for a milling machine spindle? What does the code 54M stand for?
Standard milling machine taper, and the number and series of the internal taper; #50 standard taper, #4 Morse internal.
395
You want to mill a piece of stock with a 6″ cutter and a CFS of 75. At what rpm should you set the machine? Show the formula.
RPM = 4 X 75 / 60 = 50
396
What milling direction keeps the cutting forces against the lead screw?
Conventional (up) milling.
397
In climb milling, what precautions should you take? Why?
Ensure the gibs are snug, there’s no excessive backlash in the lead screw, and put slight back pressure on the lead screw; to help keep the backlash out and the workpiece from being pulled into the cutter.
398
What is the normal range of chip thickness for general milling?
From 0.001 to 0.015″.
399
You are milling a part with a cutter that has 15 teeth. The rpm is set at 50. With a feed of 1.50 ipm, how thick will the chip be?
T=1.50/15X50=0.002"
400
If you have selected a 16-tooth cutter for a milling operation that requires a speed of 60 rpm and chip thickness of 0.006″, what should the feed setting be?
Feed=0.006X16X60=5.76 ipm.
401
What is the purpose of plain milling?
To mill a flat surface parallel to the cutter’s axis.
402
When you plain mill, at what depth of cut should you begin roughing?
0.100 to 0.200″.
403
In plain milling, what’s the relationship between the cutter and workpiece?
Use a cutter slightly wider in the diameter than the workpiece.
404
What is the purpose of face milling?
To mill surfaces perpendicular to the cutter’s axis.
405
In face milling, how does the cutter diameter compare to the thickness of the work?
The diameter should be larger than the work’s thickness.
406
When you mill workpieces mounted in machine vises, where should you direct the thrust of the cutter?
It should be positioned so the thrust of the cutter is down and toward the solid jaw.
407
What are two ways to do angular milling without setting the cutter at an angle or using angular milling cutters?
Any two of the following: (1) Use the toolmaker’s knee to position the work at the required angle to the cutter. (2) Use angular parallels to support the work at an angle to the cutter. (3) Tilt the machine’s vertical head to the angle and use an end mill or shell milling cutter. (4) Mount the workpiece on an angle plate.
408
How do you align the head of a vertical milling machine?
Mount the dial indicator on the machine spindle with the plunger in light contact with the machine table; take readings at 90° intervals on the table and record the runout; and adjust the head by loosening the head bolts and adjusting the runout––first in the machine’s lateral direction, and then in the machine’s longitudinal direction.
409
What milling operation would you use as a preliminary step for keyseat cutting, drilling, or boring?
Plunging.
410
What’s a parallelogram slot? How can you prevent it?
It’s a slot that has sides parallel to each other, but not perpendicular to the bottom; increasing the spindle speed and decreasing the feed rate so the chip load on each tooth is reduced, or decreasing the length of the end mill projecting from the spindle and using an end mill with more teeth.
411
What does an offset boring head permit you to do?
To bore holes accurately on a milling machine and adjust the cut at right angles to the spindle axis so you can enlarge holes.
412
For what operations can you use a fly cutter?
Form cutting (gear teeth, splines, etc.); boring; and plain, face, and angular milling.
413
How can you machine gear teeth with a fly cutter?
As long as you have a usable portion of the gear, you can grind a form cutter to cut teeth.
414
How do you mount fly cutters for boring? For facing?
Through the arbor and lock in place with a setscrew; on the end of the arbor.
415
What’s the difference between a keyseat and keyway?
A keyseat is a groove milled in a shaft; a keyway is a groove milled in the mating part.
416
To center the cutter over the work for milling a keyseat, you have picked up the side of the shaft with the side of the cutter and lowered the table. How far should you move the table?
Move it one-half the shaft diameter, plus one-half the cutter width.
417
What two dimensions must you consider when you calculate the total depth of cut for a straight external keyseat?
The depth of the keyseat and the height of the arc.
418
What’s the depth of the keyseat for a ¼″ key?
0.125″.
419
What is the caliper reading (M) over the Woodruff key and the shaft when the shaft measures 1″, the key width is ¼″, and the height of the arc is 0.018″?
M=1+0.250/2-0.018-1.107"
420
How do you align the index head with the milling machine longitudinal axis?
By aligning keys in the table slots.
421
Through what range can you set the swivel block?
Horizontal 0 to vertical 90.
422
How are work-holding devices mounted on the index head spindle?
Taper shank tools mount in the tapered hole in the spindle, while chucks are screwed or cam locked onto the spindle.
423
How do you align the index pin with the hole circle?
Loosen the side plate stop and rotate the index plate until a hole and the pin align exactly.
424
What’s the function of closely spaced notches machined on the side of an index plate?
The notches permit you to align holes in the index plate with the index pin if you’re trying to align a previously machined surface with a cutter, but the hole in the plate doesn’t align with the pin.
425
You align the swivel block with a dial indicator and test bar. Why should you check the alignment after re-clamping?
Because retightening may cause the block to shift.
426
Which indexing method uses a hand-spindle rotation instead of the hand crank?
Direct indexing.
427
When plain indexing, how many turns and holes should you move the crank to index 16 divisions with an 18-hole circle on the index plate?
40/16 = 2 8/16 = 2 1/2 = 2 9/18 , so 2 turns and 9 holes in an 18-hole circle.
428
If the direct index pin moves four holes on a 24-hole circle, how many degrees does the plate revolve?
60.
429
How far does your work turn if the index crank makes 19 complete turns?
Each turn equals 9°, so 9° × 19 turns = 171°.
430
How many turns and holes are required to index 28⅓ using a 27-hole circle?
28 1/3 / 9 X 3/3 = 85 / 27 = 3 4/27, 3 turns and 4 holes in a 27-hole circle.
431
What milling machine attachment is very versatile and can be used for indexing, machining circles, arcs, and segments?
The rotary table.
432
What attachment increases the capabilities of the index head? Explain.
The right angle plate, which allows the index head to be positioned parallel or perpendicular to the axis of the spindle.
433
What is the purpose of the toolmaker’s knee?
It lets you hold work at different angles by using a tilting and swiveling table.
434
What’s repeatability in CNC work?
You can machine multiple workpieces to the same tolerances.
435
What are the three main components of a CNC machine?
(1) The machine. (2) The drive motor and ball screw. (3) The computer.
436
Briefly describe the Cartesian coordinate system.
It’s a system of three axes where the X and the Y axis lie in the same plane and are called co-ordinate axes, and the Z axis gives a three-dimensional aspect to an object.
437
On any machine, what’s the Z axis?
The spindle axis.
438
What axes are used for CNC mills? CNC lathes?
The X and Y axis represent table travel and the Z axis represents the spindle; the X axis is the cross slide and the Z axis is the spindle
439
On a vertical CNC mill, what does each axis represent?
Z axis is vertical (it’s the spindle), X axis is longitudinal table travel, and Y axis is lateral movement (saddle).
440
What’s program zero?
It’s the datum reference; the point from where all other measurements are made.
441
What are G-codes?
Motion and control commands that inform the controller about such things as English or metric measurements, rapid or cutting movement, or even whether the movement is in a straight line or circular.
442
What are M-codes?
Miscellaneous function codes.
443
On a CNC program, what does O stand for?
Indicates the program number.
444
When creating a part in CAD, where is the X0.0, Y0.0, Z0.0 usually located?
The bottom left corner of the part.
445
If you construct a part with different line segments, why is it important to ensure the end points begin and end at the same point?
If the start point and end point of lines are not in the same place, it can cause problems when converting the lines to tool paths.
446
What tool do you use to create holes when creating a CAD drawing?
The circle and radii tool.
447
How can you eliminate unnecessary segments of geometry used to create a drawing?
By using the trim feature.
448
Curves that form a continuous loop are known as?
Closed boundary curves.
449
What are the basic machining processes that are applied to paths?
Pockets, bosses, profile (side) milling, holes, and bores.
450
What feature does CAD/CAM software need to help eliminate some common machining problems before machining begins?
Machining simulation.
451
Converting a completed CAD/CAM part to machine language (G-code) is known as?
Post processing.
452
Why is the geometry simpler for lathe parts than for mill parts?
Work turned on a lathe is always symmetrical.
453
Briefly explain how to set tool length offset.
Load the first tool, and then touch off on the top of your part and set the Z depth for this tool to zero. Repeat the process for all the tools you will use.
454
How do you set part zero when using a CNC machine?
Touch off on the sides of the part and locate the center of the spindle on the corner of the part. Set the machine to X0 and Y0.
