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