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