Parker-Majestic spindle, unusual bearings?

cyanidekid · Mar 24, 2018

I’m tearing down a ‘46 DoAll G1 grinder very with low hours, and even lower Maintenance. It has a Parker-Majestic spindle, and I just got the spindle apart.

The bearings are unusual (I think). They are a double row ball setup, but the outer races are a “flat taper” just like a tapered roller bearing. They are marked “PARKER 67 TENSION PAT. 1886219” (they differ a bit from the patent drawings though)

I’m sure this machine was never apart since built so, original equipment.

Seems like a bad design, and the fact that it disappeared quickly probably backs that up..(disassembles nicely for cleaning tho!)

Milland · Mar 24, 2018

So the balls are riding on a line contact for the outer race? I agree, that's bad unless there's no load on the system (and even then, nope).

Parker-Majestic is still around: Parker Majestic - Precision Grinders Perhaps contact them and find out if they ever offered a retrofit for that spindle to a more conventional bearing race.

cyanidekid · Mar 24, 2018

Yes, you can see the line of contact here;

Hadn’t thought to contact them, why not, worth a try!

Milland · Mar 24, 2018

Let us know what they say. You may find that the basic bearing geometry will allow for a full replacement to a more conventional angular contact bearing set, but that's more bucks than just getting a new outer race. But if there's any significant wear on the inner race it may be worth it to go full replacement.

Also find out how bearing preload was supposed to be set. With line contact, small changes in preload could have a rapid rise in contact pressures.

cyanidekid · Mar 24, 2018

yes, I will report on their response.

I thought the preload would be set with the pin drive nut and locknut on each end. they are visible in the second pic in the first post, at the top, but I think the spring in-between the two outward facing races may exert "self adjusting" preload.

I haven't pulled the races that are in the bore of the spindle to test how things stack up, ill try to get that out to answer that question.

this is an odd duck, no? cheers!

Milland · Mar 24, 2018

cyanidekid said:
this is an odd duck, no? cheers!

No odder than some idjit machinists still working at 3:30am on a Friday...

NateA2 · Mar 24, 2018

Those are indeed Early PM Precision bearings. Sadly, they are based on Ex-Cello bearings. Ex-Cello bearings (same for PM bearings) are very expensive. substantially more than metric modern AC equivalents.

Your best bet in looking for replacements is to look for Ex-Cello bearings.

I have rebuilt one or two PM OD/ID grinder workheads. Same odd early style bearings.

cyanidekid · Mar 24, 2018

as best as I can determine, they are preloaded by the spring between the two outward facing halves of the split outer race.
it is compressed toroidially (think squishing the cream cheese out of a bagel),a rather unconventional mode.

on the up side, they are in very good condition, and don't show any spalling or grooving on the races, so I can clean and reinstall.

is there any tip or trick anyone has for this type? Is grease ok?

(Milland, I'm not that odd, I had packed it in by 2;30!

)

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