AMMCO 7000 Disc Rotor Lathe - Manual (Page 15)

The scratch will usually appear as an incomplete circle. This is
caused by runout or wobble due to rotor condition or by the way
the rotor is mounted on the arbor.
To check that the rotor is correctly mounted, loosen the arbor
nut and turn the rotor 180° by hand, (make sure the inside
adapter does not rotate along with the rotor), Fig. B 15.
Retighten the arbor nut. Turn the cross feed handwheel back
about a half turn, start the lathe and move the tool bit in to make
a second scratch cut. Stop the lathe.
If the scratch cuts are side by side, Fig. B 16, next page, the
runout or wobble is caused by the rotor condition. A dial indica-
tor may be used to compare rotor runout with manufacturer’s
specifications.
If the scratch cuts are opposite one another (180°), Fig. B 17,
the rotor may not be properly mounted on the arbor. Remove
the rotor from the arbor. Examine each adapter and the arbor for
nicks, burrs, chips, dirt, and rust. Also inspect the rotor hub for
loose or damaged bearing cups. Clean, repair, remount, or
replace as necessary.
Brake Lathes
AMMCO 7000 Brake Lathes • 9
Figure B15
Figure B16
Figure B17