Snap-on • 11
Reconditioning Brake
Drums
Preparation
1.
Measure the diameter of the brake drum with a
brake drum micrometer.
Figure 9 – Measure drum diameter
2.
Determine if the drum will be within maximum
rebore limits after reconditioning.
Note:
Most often, the DISCARD diameter is cast into
the brake drum, not the maximum machining diameter.
3.
Inspect brake drum. Do not attempt to machine a
drum that is damaged or in poor condition.
Mounting Drums
1.
Loosen the boring bar clamp nut and push the
boring bar all the way into the clamp.
2.
Mount the drum on the arbor using the proper
adapters, cones, and spacers.
3.
Wrap the drum silencer band snugly around the
drum. Be sure it covers up to the right-hand edge.
Figure 10 – Attach silencer band
Important:
The spindle feed handwheel will not
operate unless the spindle feed engagement lever is
in the OFF position. Feed should only be adjusted
when the spindle is turning.
4.
Position the cross slide and spindle by turning their
respective handwheels to their maximum clockwise (in)
position. Then back off the cross feed handwheel 2
complete turns and the spindle handwheel 4 complete
turns.
5.
Position the boring bar by loosening the boring
bar clamp nut and sliding the boring bar inward toward
the drum until the tool bit is close to the drum.
The boring bar position is changed whenever a drum
of different diameter is machined.
The entire boring bar clamp may also be swiveled to
achieve the best cutting position.
Figure 11 – Positioning the boring bar
6.
Turn the drum by hand to make sure that every-
thing is clear.
7.
Turn the lathe ON.
8.
Advance the tool bit manually until it just contacts
the drum surface momentarily and makes a scratch cut.
Figure 12 – First scratch cut
9.
Loosen the dial lock screw on the cross feed
handwheel and set the dial to the diameter of the
drum as measured with the micrometer. Tighten the
lock screw.
This setting will be the reference used to help deter-
mine the drum recondition diameter.
Figure 13 – Set drum diameter measurement
Brake Lathes
Arrows for reading scale
Dial
Buckle Finger
Silencer Band for Drums
First
Scratch Cut
Dial Lock
Screw
