Rotor and Drum Machining

Technician A says that composite brake rotors use cast iron friction surfaces. Technician B says that the minimum machining spec is thicker than discard spec when machining a rotor to allow for wear. Which technician is correct?

Both

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?

Tech B

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?

Tech A

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

False

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

True

Rotor finish is measured in _______________________.

Microinches

The lower the Ra of a rotor, the _______ the surface

smoother

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°, and retightened. Technician B says that the rotor is not warped. Which technician is correct?

Tech B

Typical maximum rotor runout specifications are ______________________.

0.003 - 0.005” (0.08 - 0.13mm)

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

0.0003 - 0.0005” (0.008 - 0.013mm)