DIYbanter - View Single Post - Millrite MVI spindle bearing repair

Joseph Gwinn

In article ,
wrote:

On Sep 1, 8:51*am, Joseph Gwinn wrote:
This is a followup to "Millrite MVI spindle bearing repair - first report"
posted on 16 August 2010.

The Millrite is back together, and was improved by the experience, although
the
runout is unchanged.

For all the discussion of tapping bearings onto the spindle, I never could
get
it to work, and ended up using a length of 1/2-13 allthread, some black
iron
pipe and machined cast-iron pipe fittings, and various washers (some
shopmade)
to push the bearings back onto the spindle, and to fully seat the spindle
plus
taper roller bearings assembly back into the quill, which was still in the
MVI.

I also slightly reduced (by perhaps a tenth) the spindle diameter under the
upper bearing (farthest from the spindle nose) by careful manual sanding
and
polishing, using sandpaper and crocus cloth backed with a piece of 0.125"
thick
stiff red rubber gasket material from the local hardware store. *The
backing is
intended to ensure that sanding and polishing preferentially flattens any
scratch ridges and other peaks. *Roughing the surface slightly also helps
with
grease retention, making for easier sliding while pushing bearings into
place. *
It is now possible to adjust the preload by turning the round nut on the
spindle.

I suppose that tapping might work if the quill were on a bench, but proved
hopelessly awkward with quill in the mill. *I've certainly installed plenty
of
automobile wheel bearings by tapping, but for the spindle I was not able to
keep
the bearing race from cocking and jamming, and gave up.

A big arbor press would also have worked, had the quill been removed.

I didn't want to remove the quill because I would have to disassemble and
later
reassemble the quill DRO assembly.

The spindle now runs very quietly - the funny noises that started this
exercise
are now gone. *Only the two taper roller bearings were touched, so their
lack of
lubrication and contamination with grit were the cause. *The races and
rollers
all look OK, despite the abuse. *

Milling finishes are much improved, especially when climb milling, probably
because the dirt is gone and the preload is now correct, so the spindle
cannot
squirm around so much any more. *

Also, there was some axial play that is now gone, as the big quill nut is
now
fully tight. *

Runout is unchanged. *Near the spindle, with a drill blank clamped into a
fancy
3-jaw chuck, I measure 0.001" total runout, and 0.002" runout about 6" from
the
chuck. *This is essentially what I measured before taking the spindle
apart.

For the record, the specs are 0.0005" total runout near the spindle nose,
and
0.001" at 8" from the spindle nose, using a test bar. *A machine made in
1965
need not apologize for having only twice the runout it had in its youth.

Part of the problem is that I get (and got) different answers with each
chuck,
and have no way to know which to believe, if any. *Sometimes I get very low
runout values (in the tenths), sometimes large values (a few mils). *Test
bars
work, but are expensive, so I'm looking for an alternative. *Until this is
figured out, I won't attempt to high-spot align the bearing races.

The existing Timken bearings were high-spot marked, but the marks had been
rubbed off both outer races, probably because the quill nut was not tight
enough, allowing things to move. *

Anyway, when I have an adequate way to measure spindle runout, I will
simply try
different outer race orientations and keep the best, as removing and
replacing
the spindle with bearings is actually fairly easy. *

The trick to getting the spindle assembly out is to use a bit of allthread
passing through the spindle, one end screwed into a T-Nut in a table slot,
the
other end with washer and nut bearing on the top of the spindle, then crank
the
table down and/or the quill up to extract the spindle from the quill. *A
piece
of wood between spindle and table will prevent loose spindle hitting table.
*An
extra washer and nut just under the spindle would also work.

Joe Gwinn

For testing chucks, I've always used selected dowel pins, 1/4" ones
are fairly easy to come by if not really, really long. May not be
good enough if you're trying to reduce runout to fractions of tenths.

Yes, I've done that too, but using drill blanks.

But, now we are trying to measure the spindle runout, not chuck runout.

Joe Gwinn