14 • Snap-on
Brake Lathes
Reconditioning Disc
Brake Rotors
Preparation
1.
Inspect the rotor carefully for scoring, rust ridges
(at the inner and outer circumference of the rotor), and
hard spots. Any excessive wear or deformity should
be noted and, if not within acceptable limits, the rotor
should be replaced.
2.
Use a micrometer to check the thickness of the
rotor at no less than 3 points around the circumfer-
ence about 1" (2.54 mm) in from the outer diameter.
If the rotor thickness varies between readings, it
should be reconditioned. However, if the thickness is
less than the minimum established by the manufac-
turer, or if it will be less after reconditioning, the rotor
should be replaced.
Note:
Most often
the DISCARD thick-
ness dimension is
cast or stamped into
the rotor, not the
minimum machine-to
thickness.
Figure 15 – Measure rotor thickness
Model 6950 Twin Cutter
1.
Mount the twin cutter on the cross feed with the
stud bolt extending through the cast slot. The slot
helps center the twin cutter to the rotor.
2.
Secure the twin cutter to the cross feed with self-
aligning nut and washer assembly. Tighten the nut
firmly.
Figure 16 – Install the twin cutter
Rotor Mounting
Review the descriptions of mounting a brake drum
on page 12 and the illustrations of typical rotor mount-
ing configurations on page 15. The same directions
apply when mounting a brake rotor. Hubbed rotors are
mounted on adapters that fit into the bearing races.
Hubless rotors use a cone in the center hole and a
hubless adapter on each side of the rotor. Spacers are
used to fill out the arbor shaft so that the arbor nut can
be tightened. The setups illustrated are typical of the
many mounting configurations necessary to meet the
requirements of brake rotor reconditioning. The
adapters, cones, and spacers supplied with the lathe
will allow reconditioning of the majority of the rotors
found on current production vehicles. Optional
adapters, cones, and spacers are available to meet
special needs.
Note:
Adapters may also be used as spacers to fill
out the arbor shaft if care is taken to prevent damage
to their machined surfaces.
The patented self-aligning spacer prevents diagonal
thrust on the adapters. The self-aligning spacer should
always be used adjacent to the arbor nut.
Micrometer
Upper and lower
boring bar clamps
Cross slide self-aligning nut/washer
Twin cutter
Cross slide self-aligning nut/washer