AMMCO 3860 Drum & Disc Brake Lathe - Manual (Page 15)

AMMCO 3850, 3860 Brake Lathes • 9
Brake Lathes
11. Back the tool bit off, turn the lathe off, and
check the drum mounting. Loosen the arbor nut and
rotate the drum 1/2 turn (180°) on the arbor. Do not
allow adapters to turn with the drum. Retighten arbor
nut.
12. Turn handwheel 1/2 turn in either direction. Turn
the lathe on, advance the tool bit to make a second
scratch cut, back the tool bit off, and turn lathe off.
Figure 11 - Second Scratch Cut
If first and second scratch cuts are opposite on
another (180° apart), remove the drum from the
adapter. Check drum, adapters, and arbor for nicks,
burrs, or chips. Clean all mounting parts and surfaces
and remount the drum.
If scratch cuts are side by side, mounting is good and
the drum is ready for reconditioning.
13. Turn lathe on and position the tool bit so it just
touches the drum surface. Turn clockwise to advance
the tool bit to the inside corner of the drum.
14. Tighten the crossfeed slide lock knob.
Figure 12 - Lock Slide and Engage Feed
15. Hold the end knob of the tool bar micrometer
still, and turn the inner dial to zero.
Cuts may be .002"—.010" deep. A rough cut should
be no more than .010", a finish cut should be no less
than .002".
A cut of .002" from an 8" drum will result in a refin-
ished diameter of 8.004".
Note: A round, smooth, flat drum may require only a
finish cut .002"—.004" deep.
16. Turn the end knob of the tool bar micrometer
clockwise to set the tool bit to the desired depth-of-
cut (not more than .010" deep).
Important: Read and understand the description of
Negative and Positive Rake bits on page 3.
Never operate the lathe with a worn or bro-
ken tool bit. This may cause the tool bit
holder to contact the drum or rotor surface.
The drum or rotor, as well as the tool itself,
may be damaged. Replace worn or broken
tool bits immediately.
Important: Care must be taken to check actual drum
diameter before reconditioning so that the maximum
rebore limit established by the manufacturer is never
exceeded.
17. Lift engagement lever to engage the drive and
begin the cut.
18. When the tool bit clears the outer edge of the
drum surface, push the engagement lever down to
stop the feed.
19. Turn the lathe off and inspect the drum. Do not
remove the drum from the lathe.
20. If the first cut has not cleaned the entire brake
surface, leave the tool bar locked in position. Turn the
lathe on and slowly turn the handwheel clockwise to
move the tool bit back into the drum. Advance until
the tool bit touches the bottom of the drum and
scrapes. Turn the handwheel counterclockwise until
the scraping stops. Repeat steps 16 through19.
21. Remove the reconditioned drum, spacers, and
adapters from the lathe. Clean metal and cutting
debris from the adapters, spacers, arbor, and lathe.
CAUTION
MODEL 3860 ONLY
(STEPS 11 THRU 21)
Tighten Lock Knob
Lift to
Engage Feed