Jet J-720R, Operating Instructions And Parts Manual

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8.21 Arm/spindle control lever
The four-position control lever (Figure 7-1) controls
spindle rotation direction and raising and lowering
of arm.
The ability to control arm height is available when:
1. Main power to machine is ON at its branch
service panel.
2. E-Stop button is disengaged.
3. Arm/spindle control lever is pushed up or
down.
4. The upper locking handle has been released.
NOTE: The control lever does not return to neutral
when released, but remains in position. This
means unless you push it to neutral, the arm will
keep rising or lowering until it contacts a limit
switch.
9.0 Adjustments
After extended use, usually several years, the
radial arm drill may require adjustment of certain
parts. These areas require particular attention:
 Column locking handle (clamping force)
 Gap (backlash) between head and rail.

Feed lever/clutch engagement

Spindle travel range
9.1 Clamping force
1. Turn machine OFF and press E-stop button.
2. Release locking handle (Figure 5-1).
3. Loosen socket head screw (A, Figure 9-1).
4. Rotate adjustment nut (B) one turn clockwise.
5. Tighten screw (A).
6. Tighten locking handle (Figure 5-1).
Figure 9-1
9.2 Head/Rail Backlash
If backlash appears between gearbox head and
arm rail, the tightness between rail and bearings
can be corrected, as follows.
1. Remove cam shaft cover (#21, Figure 5-2).
2. Loosen set screws (D, Figure 9-2).
3. Insert hex key into hole (E), and rotate bearing
shaft. Rotate handwheel to move head along
rail; it should be snug but still easily turned.
4. Tighten set screws (D).
5. Repeat steps 1 through 4 for opposite side of
head.
6. Back at the original side of head, loosen set
screws (F, Figure 9-3).
7. Insert hex key into hole (G) and rotate bearing
shaft. Test handwheel tightness again. When
satisfied, retighten set screws (G).
8. Install cam shaft cover.
Figure 9-2
Figure 9-3