AMMCO 3860 Drum & Disc Brake Lathe - Manual (Page 22)

16 • AMMCO 3850, 3860 Brake Lathes
Brake Lathes
Gib Adjustment
Accurate gib adjustment is required for smooth and
accurate operation.
Gib adjustment requires patience and time. A
“rushed” gib adjustment will result in poor lathe per-
formance, poor reconditioning, reduced tool life, and
other long-term lathe problems. The gib is adjusted at
the factory and should only require adjustment for wear
after long periods of use.
1. If a twin cutter is mounted to the lathe, remove it
now.
2. Install the boring bar on the tool slide. Position the
boring bar perpendicular to the lathe spindle (pointing
away from the lathe).
Note: These instructions will use the boring bar as a
lever during gib adjustment. By lifting up on the boring
bar, any movement in the gibs will be amplified for eas-
ier identification and correction.
3. Secure the boring bar with the self-aligning nut.
Tighten self-aligning nut securely.
4. Place the handwheel in drum position.
5. Fully loosen the red lock knob on the front of the
tool slide.
6. Securely tighten the red lock knob on the cross-
feed tube (on the lower right of the crossfeed assem-
bly).
Note: This will eliminate any movement in the cross-
feed gibs. Crossfeed gib movement will interfere with
the detection and correction of looseness in the tool
slide gibs.
7. Position the tool slide squarely on the gibs. It must
not overhang the gibs at either end.
8. Check for looseness in the tool slide by pushing up
and down on the boring bar. If looseness is detected,
continue to step 9. If no looseness is detected, con-
tinue to step 13 for crossfeed gibs.
Note: The boring bar will amplify the looseness in the
gibs to make it easier to find and correct.
9. Loosen the jamb nuts on the front of the tool slide
with a 1/2 inch wrench.
10. Adjust the set screws inside the jam nuts until
the looseness is eliminated and the tool slide moves
smoothly with only moderate force. Use a 5/32 inch
allen wrench on the set screws.
Note: Check for tool slide looseness by pushing up
and down on the boring bar. Check this frequently while
adjusting the set screws.
Note: Check the movement of the tool slide by turn-
ing the handwheel to the left and right. The tool slide
should move smoothly with only moderate effort
required to turn the handwheel.
11. Once looseness is eliminated and the tool slide
moves smoothly, hold the set screws in place with the
allen wrench and tighten the jam nuts down securely
with the 1/2 inch wrench.
12. Recheck the tool slide for looseness and smooth
movement. Adjust again if looseness is felt or tool slide
movement is jerky or difficult.
Note: If the tool slide jerks or more than a moderate
amount of effort is required to turn the handwheel, the
adjustment is too tight.
13. Loosen the self-aligning nut and turn the boring
bar counterclockwise. The tool bit must be pointing
towards the belt cover on the lathe.
14. Tighten the self-aligning nut down securely.
15. Lock down the tool slide by tightening the red
lock knob down securely.
16. Place handwheel in rotor position.
17. Remove the red lock knob on the crossfeed
tube.
18. Check the crossfeed for looseness by pushing
up and down on the boring bar. If looseness is felt, con-
tinue to step 19. If no looseness is felt, no further
adjustment is required (go to step 24).
19. Loosen the jam nut next to the red lock knob
(removed in step 17) with a 9/16 inch wrench.
20. Tighten the set screw in the middle of the jam
nut with a 3/16 inch allen wrench.
21. Recheck looseness by pushing up on the boring
bar. If looseness is still present, continue tightening
down on the set screw.
22. Once looseness has been corrected, hold the
set screw in place with the 3/16 allen wrench and
tighten the jam nut down with the 9/16 inch wrench.
23. Check for smooth crossfeed movement by turn-
ing the handwheel left and right. Adjust again if the
movement is jerky or difficult.