Spindle Bearings - Precision matthews PM-833TV Manual

ADJUSTING THE R8 LOCATING SCREW
If any of your R8 holding devices cannot be inserted into
the spindle, rotate the spindle by hand to expose the
locating screw in the quill body.
2 mm hex key (ideally not a ball-end type) to help pre-
vent accidental dropping of the set screw if it comes free
from the spindle. Magnetize the key by rubbing it back
and forth against a rare-earth, or other powerful magnet.
To be on the safe side, insert a U-shape cup of thin alu-
minum scrap in the quill slot, Figure 4-12. Back out the
screw a turn or two until the problem R8 device can be
smoothly installed.
Figure 4-12 Prevent accidental loss of the locating screw
The shop-made cup, arrowed, is an 0.020" aluminum scrap.
If you sense that the set screw turns too freely, it may be
desirable to remove it completely, degrease it and the
tapped hole, then reassemble with
locker such as Loctite 242.
Depending on the thread locker, you will probably have
a few minutes to test various settings of the screw — to
accommodate all R8 devices on hand.
REMOVING THE QUILL ASSEMBLY
The quill assembly is heavy, and will damage the
table if allowed to fall. When working on the quill
protect the table with 3/4" ply, or thicker.
Before working on the quill assembly, you will first need
to remove the return spring. Follow the directions for this
on the previous page. To remove the quill assembly from
the headstock, three other steps are required:
1. Remove the two M8 screws securing the fine down-
feed worm assembly casting; 2.
supporting the worm assembly, ease the quill pinion
shaft assembly out of the headstock; 3. Remove the an-
ti-rotation dog screw located about 4 o'clock relative to
the return spring housing, Figure 4-8.
To remove the screw, loosen its 14 mm locknut, then
unscrew using a 5 mm hex key.
When re-installing the dog screw, note that it is a close
PM-833TV 4-13-21V1.indd
Magnetize a standard
removable thread
Lock the quill! While
Lock the quill!
23
fit in the quill groove. This means that the two must be
aligned carefully before tightening. To do this, remove
(or loosen) the depth stop rod. This will allow the quill to
be turned back and forth a degree or two. Check visually
for alignment with the quill groove, then run the screw
in slowly (no tightening), taking care that it is bottoming
in the groove not on the outer surface. Tighten lightly,
then hold it backed out a half turn while securing with
the locknut. Re-install/tighten the depth stop rod. Check
movement of the quill, fully up to fully down. Be sure that
the stop rod is not rubbing on the headstock casting.
If so, ease the quill bracket clamp, then reposition the
bracket, Figure 4-10.

SPINDLE BEARINGS

The spindle runs on grease-lubricated tapered roller
bearings. These should be serviced every 500 hours of
running time. Thoroughly clean each bearing assembly
then repack with a grease such as Kluber Isoflex (auto
shop wheel bearing grease can be used as a substitute
in low-load, low rpm operations).
Do not over-pack the roller bearings!
Bearing manufacturers recommend that the free volume
between inner and outer should be no more than 30%
filled with grease. (If smothered with grease, bearings
are subject to overheating.)
Especially during the first 10 hours of running time
check that the spindle runs smoothly, without ex-
cessive heat build up (the spindle will run warm
when used at high speeds over long periods, but
should not be uncomfortably hot). Overheating can
be due to excessive grease, see above, or an over-
tight spanner nut at the upper end of the spindle.
Call Precision Matthews for guidance.
MODIFYING THE DRAWBAR
Some versions of the PM-833TV have been shipped
with an over-long drawbar, Figure 4-13. The cap doesn't
touch the splined spindle, even when the drawbar screw
is threaded into the R8 device as far as it will go. This is
easily corrected by inserting a collar of 7/16" clearance
ID between the hex drawbar cap and the spindle, OR
(preferred), shortening the drawbar as follows:
1. Tap the roll pin out of the hex head. Leave the hex
head in place for the moment.
2. Wrap the drawbar with markable (masking) tape in
the region about 1/2" below the hex head.
3. Remove the hex head, then screw the drawbar into
an R8 device as far as it will go.
4. Push the R8 device up into the spindle to its ful-
ly-seated position.
5. Unscrew the drawbar 4 or 5 turns, then mark the tape
Copyright © 2021 Quality Machine Tools, LLC