Clausing spindle bearings-help!

Terry Keeley · 2005-12-01T14:20:18+00:00

I'm restoring my 1963 Clausing 8520 mill ( pictures here if interested )and in the process am replacing the spindle bearings. I've read throughmany posts on the Yahoo Group and have just gotten more confused.Talked to a few bearing "engineers" (ya right) at SKF and they don't seem tohave solid answers either.The spindle takes a pair of 7205 angular contact bearings that are held inplace by a locking washer and nut. I was able to find on the MRC site thatthe torque on the nut should be 23-50 ft-lb. but can't seem to find answersto the following:Should the bearings be mounted "face to face" (where the contact lines ofthe bearings converge inward), or "back to back"?I can order bearings that are ground and sold as a matching set in either "bto b" or "f to f" that when mounted together and the retaining nut tightenedgive a "light preload".I can also order bearings that are not matched but are for "universalpairing" that are about half the cost and are made to mount either way.Some posts on the Yahoo Group mention that to apply a preload to thesebearings a shim is needed between them either on the inner or outer race,others say none is needed. If the bearings are made to mount either way howcan they be preloaded without the use of a shim? If needed how thick shouldit be?The machine came fitted with standard bearings and no shims so I can't go bywhat was there.Any experts here? Thanks in advance!

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Ned Simmons 20 years ago

Yeah, I just looked in the HLVH manual. I don't know how I got it in my head that it's a cartridge spindle, unless on account of a Rathbone chucker I once had which was a functional copy of an HC. The Rathbone did have a cartridge. A functional copy in that all the HC tooling and attachments fit - it was constructed more like the Monarch chucker with round ways.

But there is a separate spacer that appears to be pinned in the headstock casting that separates the bearings' outer races.

I don't disagree, but think the bearing's radial looseness is a more likely culprit. Barden recommends a transition fit, around .0002 either side of line to line, for the housing in this situation. I'd describe the housing fit on the 3rd bearing in the few spindles I've had apart as a wringing fit - tighter than a slip fit, but moves with firm hand pressure. In either case, movement due to radial clearance in the bearing itself or radial movement of the bearing in the bore, you'd expect to see a knee in a force vs. deflection curve. I mentioned in an earlier post in this thread that I was able to see the effect of the radial bearing in a BP spindle by measuring the difference in deflection at the nose with the top radial bearing both removed and installed, but I don't recall checking for a change in stiffness as the top bearing loads up. So I just did a quick test with a spring scale and indicator on the BP.

I mounted a 50 millionths indicator on an Indicol holder clamped to the spindle collar and placed the probe on the OD of the quill. A spring scale was clamped in the vise and arranged to push on a rod held in a drill chuck. Cranking the table allowed me to apply a controlled force while monitoring deflection. I *may* have been able to see the expected effect, but the deflections were much too small to measure reliably - even with the force applied about 5" below the spindle nose, a 60# load only moved the spindle about .00015 relative to the quill. It *looked* like the first .00005 occurred at about 10# load, but it'd take much better resolution to be sure.

Ned Simmons

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jim rozen 20 years ago

Interesting, I've never seen an exploded diagram for one of those, nor have I had one that far apart. A steel cylinder pinned into the casting would indeed eliminate the thermal expansion issue to a large degree, and likewise put all the "sin" in getting the OD race separation away from the rough headstock casting, into something that could be more tightly controlled during manufacture. All things that hardinge could be expected to figure out, and implement.

Yep, that's just about what I felt when I removed the spindle from that BB headstock lathe.

Interesting test. If I could figure out a way to take home my federal electronic indicator, I could try that in the hardinge. Of course, that may well have a preload spring for the rear radial bearing, if Jim Schwitter's diagram matches that machine.

Jim

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Gunner Asch 20 years ago

Correct

Gunner

"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.

Think of it as having your older brother knock the s*it out of you for torturing the cat." Gunner

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Gunner Asch 20 years ago

There is indeed a cylinder inside the head, but its a hard pressfit into the headstock casting and pinned via a steel taper pin from top dead center of the headstock. I actually broke one free from a headstock that had a heavily rusted in bearing. Using my 20lb bearing knocker with a 10lb sledge sorta got it moveing...

But IRRC..the cylinder doesnt contact the outer race. Ive still to do that DV-59 yet...Ive had pnuemonia ..sigh and Ill check carefuly when I yank the spindle.

Gunner

"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.

Think of it as having your older brother knock the s*it out of you for torturing the cat." Gunner

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jim rozen 20 years ago

It would make sense to me if it did (contact the outer races) because that would be one way for them to eliminate the thermal differential expansion issues.

Pneumomia is nothing to fool with. I've noticed you were sparse around here lately. That's the sort of thing you have to watch for or you will end up in the hospital for a while - like ms. Mulligan did two years ago. Hope you are on the mend.

Jim

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