Deck 104: Machining Brake Drums and Rotors

Question 1

Technician A says that aluminum brake drums use cast iron friction surfaces. Technician B says that up to 0.030 in. (0.8 mm) should be left after machining a drum to allow for wear. Which technician is correct?

A)Technician A only
B)Technician B only
C)Both technicians A and B
D)Neither technician A nor B

Answer 1

Both technicians A and B

Question 2

Technician A says that hard spots in a brake drum should be removed using a carbide-tip machining tool. Technician B says that the drum should be replaced if hard spots are discovered. Which technician is correct?

A)Technician A only
B)Technician B only
C)Both technicians A and B
D)Neither technician A nor B

Answer 2

Technician B only

Question 3

Technician A says that brake drums on the same axle should be close to the same inside diameter for best brake balance. Technician B says that a brake drum may be cracked if it rings like a bell when tapped with a light steel hammer. Which technician is correct?

A)Technician A only
B)Technician B only
C)Both technicians A and B
D)Neither technician A nor B

Answer 3

Technician A only

Question 4

A hubless brake drum cannot be machined because it cannot be held in a lathe.

Question 5

The major reason for brake pedal pulsation during braking is due to excessive rotor thickness variation.

Question 6

Rotor finish is measured in ________.

A)Inches
B)Centimeters
C)Millimeters
D)Microinches

Question 7

The lower the Ra of a rotor, the ________ the surface.

A)Higher
B)Lower
C)Smoother
D)Rougher

Question 8

A disc brake rotor is being installed on a lathe for machining. During the setup a scratch test is performed. The scratch extended all the way around the rotor. Technician A says that the rotor should be loosened, rotated 180 degrees, and retightened. Technician B says that the rotor is not warped. Which technician is correct?

A)Technician A only
B)Technician B only
C)Both technicians A and B
D)Neither technician A nor B

Question 9

Typical maximum rotor runout specifications are ________.

A)0.003 to 0.005 in. (0.08 to 0.13 mm)
B)0.300 to 0.500 in. (8.0 to 13 mm)
C)0.0003 to 0.0005 in. (0.008 to 0.013 mm)
D)0.030 to 0.050 in. (0.8 to 1.3 mm)

Question 10

Typical maximum rotor thickness variation (parallelism) specifications are ________.

A)0.030 to 0.050 in. (0.8 to 1.3 mm)
B)0.0003 to 0.0005 in. (0.008 to 0.013 mm)
C)0.003 to 0.005 in. (0.08 to 0.13 mm)
D)0.300 to 0.500 in. (8.0 to 13 mm)

Question 11

Two technicians are discussing hard spots in brake drums. Technician A says the drum should be replaced. Technician B says the hard spots are caused by using riveted rather than bonded brake shoes. Which technician is correct?

A)Technician A only
B)Technician B only
C)Both technicians A and B
D)Neither technician A nor B

Question 12

Hard spots in a brake drum are caused by ________.

A)Machining a drum at too high a speed
B)Improper mounting of the drum on the lathe
C)Excessive heat and pressure
D)Machining a drum without using a rubber belt to damper out the vibrations

Question 13

Two technicians are discussing the machining of brake drums. Technician A says that most brake drums cannot be machined more than 0.060 in. oversize. Technician B says that brake drums on a common axle should be machined to within 0.010 in. of each other. Which technician is correct?

A)Technician A only
B)Technician B only
C)Both technicians A and B
D)Neither technician A nor B

Question 14

Two technicians are discussing disc brake rotor service. Technician A says that the inner races (bearing cups) should be removed from the rotor before it is mounted on the lathe. Technician B says that a non-directional finish on the rotor surfaces can be obtained by using sandpaper. Which technician is correct?

A)Technician A only
B)Technician B only
C)Both technicians A and B
D)Neither technician A nor B

Question 15

Technician A says heat checking can be caused by numerous panic stops in rapid succession. Technician B says it can be caused by "riding" the brake pedal. Which technician is correct?

A)Technician A only
B)Technician B only
C)Both technicians A and B
D)Neither technician A nor B

Question 16

Which is NOT a type of brake drum construction?

A)Centrifugally cast
B)Bimetallic
C)Solid composite
D)Composite

Question 17

Which one is not a form of drum distortion?

A)Out-of-round
B)Lack of parallelism
C)Bellmouth
D)Eccentric

Question 18

Most manufacturers specify that the friction surfaces of a rotor must be parallel to within ________.

A)0.005 inch (0.127 mm)
B)0.0001 inch (0.0025 mm)
C)0.001 inch (0.0254 mm)
D)0.0005 inch (0.013 mm)

Question 19

The chamfer on the inside edge of a brake drum usually indicates ________.

A)Machine to diameter
B)Maximum allowable inside diameter
C)Aluminum drum with cast iron inset
D)Bi-metallic drums (1/2 cast iron and 1/2 steel)

Question 20

Technician A says anti-vibration devices only need to be used when resurfacing drums. Technician B says composite brake rotors require special adapters when mounted on a bench lathe for resurfacing. Which technician is correct?

A)Technician A only
B)Technician B only
C)Both technicians A and B
D)Neither technician A nor B

Question 21

Technician A says there are no brake lathes that can machine rotors on the vehicle. Technician B says drums may be removed from the vehicle to be machined. Which technician is correct?

A)Technician A only
B)Technician B only
C)Both technicians A and B
D)Neither technician A nor B

Question 22

The rotor in this illustration was measured in three places.
The measurements are:
Point A = .987 "
Point B = .986 "
Point C = .987 "
The minimum thickness specification is .968 ". The rotor surface is smooth and not scored. What action should the technician take?

A)Replace the rotor.
B)None, the rotor is OK.
C)Drive the vehicle to see if the variation evens out.
D)Machine the rotor to correct the thickness variation.

Question 23

What is the reading on this micrometer?

Question 24

What is the reading on this micrometer?

Question 25

What is the reading on this micrometer?