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CDC 2A751- SSgt > CDC VOl 2. > Flashcards

CDC VOl 2. Flashcards

1
Q

What is your goal when constructing a drawing?

A

Complete the drawing accurately and be timely

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2
Q

What three things can you do to make drawing more comfortable and improve your
work?

A

Arrange your equipment systematically, place items for easy reach and in the same areas when not in use, and keep the equipment clean.

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3
Q

Name the basic equipment items used for drafting

A

Drawing board, T-square, triangle set, scale, pencil, protractor, eraser, and a set of drafting instruments.

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4
Q

What should you use to sharpen the point of a wooden drawing pencil?

A

Sandpaper or a pencil pointer.

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5
Q

Which type of erasers is preferred for use when drafting?

A

Art gum and pink pearl.

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6
Q

What are the two most common types of scales used?

A

Engineer’s and architect’s.

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7
Q

As a minimum, which instruments should your drawing set include?

A

One pair of large dividers, one large compass, one small bow compass, one small bow divider, compass leads and spare points.

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8
Q

Which instrument do you use to transfer measurements and distances?

A

Divider.

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9
Q

What are dimension lines?

A

solid black lines terminated at each end by an arrowhead, indicating the dimensions of a space.

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10
Q

Describe what the lines below represent:

a. Datum lines:
b. Viewing plane lines:
c. Border lines:

A

a. Show surfaces not present in the drawing where reference points or positions are located
b. Show the plane or degree from which the surface is viewed.

c. Extra heavy lines that frame the entire drawing.
Show surfaces not present in the drawing where reference points or positions are located.

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11
Q

If you cannot immediately identify a dimension as a diameter, what should you do?

A

Place the abbreviation DIA after the number.

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12
Q

What are the identifying symbols for location, size, and radius?

A

L-location, S-size, R-radius.

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13
Q

Define the following contour dimensions:

a. Chamfer.
b. Countersink.
c. Counterbore.

A

a. A beveled external or internal edge.
b. A conical depression to accommodate a screw head.
c. A recess at the top of a drilled hole; permits clearance for a nut or bolt.

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14
Q

How do you dimension slots with rounded ends in a drawing?

A

Give the overall length and width of the slot, plus the radii.

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15
Q

What information would you include when dimensioning threads?

A

The diameter of the thread, TPI, thread series, and class of fit.

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16
Q

What is tolerance?

A

The difference between the allowable minimum and the allowable maximum dimension

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17
Q

What is an allowance?

A

An intentional difference in dimensions of mating parts.

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18
Q

What is the difference between clearance allowance and interference allowance?

A

Clearance allowance permits movement between mating parts when they’re assembled; whereas, interference allowance is a tight fit.

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19
Q
  1. Define the symbols listed below:
    a. Welding symbol.
    b. Weld symbol.
A

a. Welding symbol give all of the information you need for a print: reference line, arrow, basic weld symbol, dimensions, supplementary symbols, tail, specification and process.
b. Weld symbols give the type of weld (e.g., square grove, fillet, etc.) and its shape or contour.

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20
Q

What do supplementary weld symbols designate?

A

Requirements common to many welding processes, which consists of symbols such as field, flush, and convex contour welds.

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21
Q
  1. Define the following CAD tools:
    a. Vertical lines tool.
    b. Connected lines tool.
    c. Trim or extend tool.
A

Creates an unbounded (without termination points) vertical line through the point you chose.

b. Creates lines that are defined by endpoints but the last endpoint entered will be the start point of the next line.
c. Changes the length of a line or arc.

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22
Q

What is the function of a grid when used in CAD drawings?

A

Overlays the display screen with a grid pattern of any desired size and it is used as a guide to help construct geometry accurately.

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23
Q

What are the four main benefits of CAD?

A

Speed, quality, editing ease, and storage.

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24
Q

What information will you find in the title block of a blueprint?

A

Material, heat treatment required, specified tolerances, finish notes, drawing scale, print identification, and bill of materials.

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25
Q

How are notes positioned on a print?

A

So they are read from left to right and parallel to the bottom of the print.

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26
Q

What are the three common types of notes? Describe them.

A

Local notes apply directly to a particular part of a drawing. General notes apply to the overall drawing in general. Indexed notes apply to specific areas on the drawing, cross referenced to a parts list on the print.

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27
Q

What is a TO working drawing?

A

A guide you use to manufacture items such as special tools.

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28
Q

What is a TO assembly drawing?

A

A drawing that contains partial or complete assemblies, instead of one or two parts with specific dimensions except overall, center, and dimensions relating to other parts or assemblies

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29
Q

Describe the following terms:

a. Unit assembly drawing.
b. Maintenance assembly drawing.
c. Exploded drawing.

A

A) Unit assembly drawing shows a completely assembled unit, you can see all parts of the unit.

B) Maintenance assembly drawing shows units in the process of assembly.

C) Exploded drawing shows the relationship of parts in a unit, not assembled.

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30
Q

What are the layout tools you’ll most likely need for welding work?

A

Soapstone, a square, straightedge, and tape measure.

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31
Q

What happens if you use too much layout dye?

A

It will flake and create ragged, uneven lines when scribed.

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32
Q

Name a use you can find for soapstone in welding operations.

A

Writing the word HOT to alert co-workers so they will not touch the work.

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33
Q

Which type of tool material is known to respond erratically to heat treatment?

A

Plain carbon steel.

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34
Q

Why are high-speed tool steels valuable in tool manufacturing?

A

They retain hardness and strength at high operating temperatures.

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35
Q

What tool material routinely performs beyond the limits of tool steels and is suitable for hard abrasive materials and hard alloys?

A

Nonferrous tool materials

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36
Q

What are some defects found in low-grade steel?

A

Seams, laminations, blowholes, erratic grain size, and uneven tensile strength.

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37
Q

What is the main cause of tool deflection?

A

Dull tooling.

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38
Q

What is the best method of keeping tool thermal expansion to a minimum?

A

By keeping cutting tools sharp and using lots of coolant.

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39
Q

Which two important areas should you consider when developing a plan to machine parts?

A

Using a materials and parts list; deciding what tools you’re going to use and how to get them

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40
Q

If you’re going to machine holes in a part, and the hole size and location are not critical, which machine would you choose?

A

A drill press.

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41
Q

What’s the technical difference between a jig and a fixture?

A

Jigs hold, support, and locate a workpiece while guiding a cutting tool. Fixtures hold, support, and locate a workpiece in relation to a cutting tool.

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42
Q

What are the two general classes of jigs?

A

Drilling and boring.

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43
Q

Which type of jig is used for limited production?

A

Template.

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44
Q

What are the limitations of using auxiliary vise jaws as fixtures?

A

The diameter of the stock, the working size of the vise, and depth of the V cut.

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45
Q

What is blanking?

A

Involves cutting out a part with a punch or die.

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46
Q

What is the difference between piercing and blanking?

A

During piercing, the punched out material is the scrap and strip is the workpiece; during blanking, the punched out piece is the workpiece and the strip becomes the strap.

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47
Q

Which type of die would you select to form aircraft structural parts

A

A bending or forming die.

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48
Q

What’s another name for a loose fit?

A

clearance fit

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49
Q

Which type of fit is used for machines running at higher speeds and with heavy journal pressure?

A

RC5 and RC6, medium running fit.

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50
Q

For what purpose are LC fits used?

A

For stationary fits where parts can be freely assembled and disassembled.

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51
Q

Which type of fit would you select to maintain accuracy, but permit a small amount of clearance or interference?

A

Locatation transitional (LT)

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52
Q

Which type of fit do you select for parts that need rigidity and extreme location accuracy?

A

Location Interference (LN)

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53
Q

What are some methods of chilling parts for interference fits?

A

Dry ice and liquid nitrogen

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54
Q

What are the general rules for determining the amount of interference fit on parts?

A

allow 0.0015 inch in diameter for bored holes

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55
Q

What is the main purpose of lubrication?

A

To reduce friction between parts.

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56
Q

What is static friction?

A

Friction between a surface at rest and one on which it rests.

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57
Q

What is kinetic friction?

A

Friction between a stationary and a moving surface, or friction between two moving surfaces.

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58
Q

Explain cohesion and adhesion in terms of fluid friction.

A

Cohesion is the attraction between the molecules of a substance that tends to hold the substance together

adhesion is the attraction between molecules that tends to cause unlike surfaces to stick together

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59
Q

Besides permitting one surface to slide over another, what other benefit does a lubricant provide?

A

It helps carry heat away from the bearing surfaces.

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60
Q

Explain the difference between a high-viscosity oil and a low-viscosity oil.

A

High-viscosity oil flows slowly in colder weather while low-viscosity oil flows quickly in warmer weather.

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61
Q

Which grade of grease do you select for slow machine speeds with heavy pressure?

A

Hard grease.

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62
Q

List the limitations of dry film lubricants.

A

They cannot carry heat away from the operating area, don’t replenish themselves like greases, and don’t adhere to the material surface the way greases do.

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63
Q

What is the main purpose of a coolant?

A

To carry away cutting tool heat.

64
Q

What is the purpose of a cutting fluid?

A

To reduce cutting forces, ease machining, lubricate materials as they are machined, and reduce friction between parts.

65
Q

What important item must you consider if you’re selecting a cutting fluid for Al?

A

Chemical reactions with some cutting fluids.

66
Q

In a machining operation where your workpiece is made of Mg, which cutting oil do you select?

A

One that does not contain any water and has a low acid content.

67
Q

What is the disadvantage of using compressed air as a coolant?

A

It does little to prevent friction and cutter tip breakdown.

68
Q

What advantage does the jet cooling method have over the other cooling methods?

A

It’s a more effective method of cooling because it forces coolant onto the tool and part contact area. This reduces cutting tool temperature and prolongs cutting tool life.

69
Q

Which saw band item refers to the saw teeth shape and spacing?

A

The type.

70
Q

On the contour machine, where are the upper and lower guide blocks mounted?

A

The upper guide block is secured to the lower end of the guide block; the lower guide block is secured to a keeper block under the table.

71
Q

How is the contour machine’s upper wheel adjusted to permit the band to track properly?

A

Loosen the tilt locknut, rotate wheel by hand using the tilt screw and upper wheel until the band tracks lightly on the guide roller; then, lock the tilt locknut.

72
Q

To select the correct speed for a sawing operation, what two things must you consider

A

1) The type of material you’re cutting.

(2) The thickness of the material you’re cutting.

73
Q

How does the recommended speed for sawing titanium and Monel differ from that for most other nonferrous metals? Give the comparable speeds.

A

The recommended speed for titanium and Monel is much slower (90–125 fpm) than for most nonferrous metals (700–1,500 fpm).

74
Q

Why should the sawing feed pressure be greater on titanium than on most other metals?

A

Because titanium does not dissipate heat quickly.

75
Q

How can you help prevent injury to your hands when applying feed pressure when sawing or filing on the contour machine?

A

The keeper block limits the angle tilt of the machine table.

76
Q

How do you check the angle of the table, other than by using the graduated plates below the table?

A

By measuring the angle formed by the guidepost and the table with a protractor head and blade.

77
Q

How do you cut a saw band prior to welding?

A

Through the gullets, from the back toward the teeth

78
Q

What safety precaution must you observe during a welding process?

A

Always wear safety goggles.

79
Q

What is the purpose of the rip fence?

A

To cut stock so sides are parallel.

80
Q

Explain the techniques for lubricating the grinder motor. How often do you lubricate it?

A

Put a few drops of oil into the cap fillers on the welder panel; about once a month is sufficient.

81
Q

With what do you lubricate the air pump?

A

Powdered graphite only, which is put into the air intake.

82
Q

Describe the techniques for correcting the problem of worn and grooved tires on the upper and lower wheels.

A

Remove them, turn them inside out, and reinstall them. If the tires are badly worn, replace them.

83
Q

What is the function or purpose of power cutoff tools?

A

To make straight, vertical cuts.

84
Q

Why are the saw bands on horizontal band saws wider and heavier than those on the contour machine?

A

To permit heavier cutting forces.

85
Q

What item keeps the saw band cutting efficiently without excessive wear?

A

The feed adjustment.

86
Q

How do you set band guides for cutting?

A

They must be as close to the work as possible to keep the band from flexing, twisting, and binding

87
Q

When using an abrasive cutoff saw, why do you support long workpieces?

A

To keep them from twisting in the machine vise or falling and causing injury or damage to the machine.

88
Q

What operations can you accomplish with the ironworker?

A

Shearing, coping, cutting, piercing, notching, and bending.

89
Q

What determines an ironworker’s capacity?What must you adjust prior to operating the ironworker? Why?

A

The pressure in psi of the cutting stroke material thickness maximum and tensile strength.

90
Q

How often should you lubricate the blade when performing cutting operations?

A

Every 10 to 15 strokes.

91
Q

What is the limitation on material thickness for blasting using silica sand abrasive?

A

Do not blast material below 0.0625 inch or soft materials.

92
Q

Which type of abrasive is highly effective for paint removal?

A

PMB.

93
Q

What is the disadvantage of using glass beads as a blasting medium?

A

They fracture after several uses, which makes them more abrasive, but less effective.

94
Q

In which forms are shot in and what is an advantage of using it as a blasting medium?

A

It can be made of ferrous or nonferrous material; it is less damaging to equipment and is efficient.

95
Q

Which type of abrasive works best for removing carbon scale from intricate workpieces?

A

Organic.

96
Q

At what point do you replace the nozzle outlet on a media blasting machine?

A

When it’s worn to 11⁄2 times its original size.

97
Q

What is the correct pressure range for media blasting?

A

15 to 60 psi.

98
Q

Why is surface distance critical? What is the correct distance?

A

If you hold the nozzle too close, it can damage the workpiece surface; too far away can slow down the cleaning process. The correct distance is 12 to 18 inches from the material surface.

99
Q

Define “dwell.” What can happen to material surfaces if you dwell too long on an area?

A

The length of time you blast in one spot on a workpiece; dwelling too long can cause the surface to develop stress concentrations and warp; on softer materials, it causes the abrasive to eat away the material surface.

100
Q

Why do you remove fluids from material surfaces before blasting?

A

They can impregnate the material surface and contaminate the blasting media.

101
Q

Why is correct masking an important step of surface preparation?

A

It keeps the abrasive material from intruding into interior surfaces and damaging or contaminating equipment.

102
Q

How do you remove the blasting media after you’ve completed the blasting process?

A

Vacuum the workpiece to remove the abrasives; use compressed air or water as an alternative.

103
Q

Which part of the grinding wheel removes the metal while grinding? Explain this process.

A

Abrasives remove material from the surface of a workpiece. Each abrasive grain acts as a separate cutting tool, removing a small metal chip as it passes over the surface of the workpiece.

104
Q

Name the two types of abrasives.

A

Natural and manufactured (artificial)

105
Q

What is one advantage manufactured abrasives have over natural abrasives?

A

Manufacturers can control grain size and shape, as well as purity.

106
Q

What are some commonly manufactured abrasives?

A

Aluminum oxide, silicon carbide, industrial diamond, and cubic boron nitride.

107
Q

Why is aluminum oxide the most common abrasive available?

A

It is manufactured in differing degrees of purity, depending on application.

108
Q

Which type of abrasive is used to grind the toughest and hardest materials?

A

Industrial diamond.

109
Q

What factors determine the grinding wheel grade you will select for a particular job?

A

The kind of material to grind, amount of stock to remove, accuracy and finish required, and contact area between the wheel and the work.

110
Q

What do you do when you receive a new wheel or remove one from storage?

A

Inspect it closely for damage and cracks.

111
Q

How do you check a wheel for cracks?

A

Tap it gently with a light nonmetallic instrument, such as the handle of a screwdriver.

112
Q

How can you tell if a wheel is cracked?

A

It is readily identifiable because of its “dead” sound.

113
Q

How do you balance a grinding wheel?

A

By shifting the balance weights’ position, which are located inside a circular groove cut in the wheel mount bushing.

114
Q

What do you need to do after mounting a new wheel on your grinder?

A

Stand to one side and let it run at full operating speed for at least 1 minute before using it.

115
Q

What does dressing a grinding wheel improve?

A

The wheel’s cutting action.

116
Q

Which dressing tool is the most efficient for truing precision grinding wheels?

A

The diamond dresser.

117
Q

Where should you store all grinding wheels regardless of type?

A

In a dry place.

118
Q

What procedure do you use for sharpening a drill bit with a pedestal grinder?

A

Position your hand on the tool rest; use your fingers as a pivot and push down on the shank of the drill bit as you “roll” the drill across the face of the wheel; keep the shank lower than the cutting edge.

119
Q

Why is it important not to raise the shank of the drill bit higher than the cutting edge while sharpening it?

A

You could grind a negative relief angle on the cutting edge.

120
Q

What happens with repeated sharpening of a drill bit?

A

You shorten the drill bit and the web thickness increases, which lengthens the chisel edge.

121
Q

What do you use to check drill point angles when sharpening them?

A

Drill point gage or protractor head and blade.

122
Q

What is the maximum allowable distance between the tool rest and the grinding wheel? Why is it important to check and adjust it often?

A

One-eighth inch. The grinding wheel wears as you use it and the gap increases

123
Q

What could malfunction if dirt is allowed to build up on a grinding machine?

A

It can get into the bearings and electrical connections, which may cause a breakdown.

124
Q

Which preventive maintenance practices do you follow concerning lubrication?

A

Refer to the lubrication schedule in the TO or manufacturer’s publication and follow it.

125
Q

When drilling, why do you allow some movement, or “float”, between the twist drill and the workpiece?

A

Allows the center punch mark to align the workpiece to the drill as it starts to drill the hole.

126
Q

How can you prevent work from climbing up the drill bit as it breaks through the lower work surface?

A

By reducing the feed pressure.

127
Q

Why does a large drill bit require a slower speed than a small one, even though the type of metal to be drilled is the same?

A

A change in drill diameter results in a change of circumference, you must change the rpm to get the same desired CFS since a smaller one has to resolve faster to cover the same area as a larger one.

128
Q

When do you not use a center drill to start a hole?

A

For smaller drill presses if the workpiece cannot float on the table and align under the spindle because any misalignment of the center-drilled hole is difficult to correct.

129
Q

Identify the safety practices to follow during drill press operation.

A

Always wear safety glasses; button or roll long shirt sleeves up past your elbows, or remove your shir

130
Q

What safety precaution do you take when you stop the spindle to put a different bit in the drill chuck?

A

Avoid stopping the chuck by grasping it with your hand.

131
Q

What is the safe way to remove chips from a drill press operation?

A

Stop the drill press and remove the chips with a brush or rag.

132
Q

How can you prevent a drill bit from producing dangerously long and stringy chips?

A

By interrupting the feed to break up the chips during the drilling operation.

133
Q

Which two items must you be most concerned with when installing a drill press?

A

Level the column to the floor and bolt the machine securely in place.

134
Q

What technique do you use when lubricating the drill press?

A

Start at one point and lubricate all points progressively around the machine.

135
Q

How can you help prevent the arm of a radial drill press from seizing on the column when you raise or lower the arm?

A

Wipe the oil film from the column and replace it with fresh oil.

136
Q

What is the advantage of using a mechanical arbor press for broaching?

A

It is sensitive enough to “feel” the pressure being applied, which can keep you from overpressing a part.

137
Q

Which two components of the hydraulic press are used to create the pressure needed to perform press operations?

A

A hydraulic cylinder and pump.

138
Q

What should you consider when beginning any press operations?

A

The interference fit between the mating parts, corrosion, marred edges, overlooked fasteners, and the part mass.

139
Q

What precautions must you take when operating a press to prevent damage to the equipment?

A

Support the work adequately; place the ram in contact with the work for accurate location and alignment; use a soft material between the press ram and work to protect the work surface; use a lubricant to prevent seizing; and release pressure and double check to find the cause of the bind if too much is applied.

140
Q

What factors determine the size of a belt sander?

A

The horsepower of the motor and the size of the sanding belt.

141
Q

What is the purpose of the backup platen?

A

Provides a large surface area behind the sanding belt for flat grinding.

142
Q

Briefly explain loose belt grinding.

A

Allows the operator to sand intricate shapes by using the flexibility of the sanding belt to wrap around contours.

143
Q

Why is it important to prevent movement of the belt tracking knob when the machine is off?

A

If adjustments are made with the machine off, when you power up the machine, the belt can quickly shift position, possibly causing injury or damage to the machine.

144
Q

How does an abrasive waterjet and pure waterjet cutter differ?

A

With the abrasive waterjet, the waterjet stream accelerates abrasive particles; those particles, not the water, erode the material. With a pure waterjet, the supersonic stream erodes the material.

145
Q

Which machine is used for cutting hard materials?

A

The abrasive waterjet.

146
Q

Which two styles of machine dominate the industry?

A

Mid-rail gantry and cantilever.

147
Q

What two types of pumps are used in waterjet applications?

A

Direct-drive-based and intensifier-based pump

148
Q

What is the most common abrasive used in waterjets?

A

Garnet.

149
Q

How is the geometry created for more complex parts?

A

Drawn using CAD software.

150
Q

How do most machines calculate feed rate?

A

After designating the material type, thickness, and finish.

151
Q

How does the geometry of the part affect the cutting speed?

A

Parts with lots of holes and sharp corners cut much slower than simpler shapes.

152
Q

What can you do if there is dirty or hard water in a waterjet?

A

Maintain everything more often, or purchase a good water softener or filtration system.

153
Q

What can happen if you get dirt in the high-pressure plumbing?

A

Becomes bullets that crack the jewel.

154
Q

What should you do after rebuilding something up-stream of the nozzle?

A

Remove the nozzle and flush the lines with low pressure before putting the nozzle back on.

155
Q

How can you minimize the mixing tube from having uneven wear?

A

By rotating the mixing tube once in a while.

CDC 2A751- SSgt (2 decks)

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