AMMCO 7700 Drum and Disc Brake lathe - Manual (Page 11)

AMMCO Drum & Disc Brake Lathes • 7
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 12 – 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 13 – First scratch cut
9. Loosen the dial lock screw on the cross feed hand-
wheel 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 14 – Set drum diameter measurement
10. Back the tool bit off and turn the lathe OFF.
11. Loosen the arbor nut, rotate the drum 12 turn
(180°) on the arbor and inner adapter, and retighten the
nut.
12. Turn the lathe ON.
13. Turn the spindle feed handwheel 12 turn in
either direction and make a second scratch cut.
Figure 15 – Second scratch cut
14. Turn the lathe OFF.
15. Examine the scratch cuts.
If the first and second cuts are opposite one another
(180° apart), remove the drum from the arbor, check
the mounting adapters and arbor for nicks, burrs, or
chips, remount the drum, and repeat scratch cut
process.
If the scratches are side by side, proceed to step 16.
16.
Turn the spindle feed handwheel until the deep-
est worn groove of the drum lines up with the point of
the tool bit.
17. Advance the tool bit into the bottom of the
groove by rotating the cross feed handwheel counter-
clockwise.
Note: These operations may be done with the lathe
running.
The depth of cut dial will show the approximate
reconditioned diameter of the drum. This measure-
ment must be compared with:
A. The maximum rebore limits cast into the drum.
B. The measured diameter to determine the best
amount of material to be removed in one pass.
18. Determine the depth-of-cut by these general
guidelines:
• Roughing cuts should be no deeper than 0.020” .
• Finish cuts should be no shallower than 0.004”
deep.
19. With the lathe running, set the depth-of-cut dial
to the depth desired and lock the cross feed by tight-
ening the lock knob.
First
Scratch Cut
Dial Lock
Screw
Second
Scratch Cut