Spindle bearing replacement

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John Hasler
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Re: Spindle bearing replacement

Post by John Hasler » Fri Jun 07, 2019 7:22 am

The question at hand is spindle runout, though, not headstock alignment. As you pointed out, the latter won't show up as runout. As you say, the slightest thing changes what you think is happening. So why not eliminate as many of those things as possible and take the runout off the inside of the spindle taper?

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NP317
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Re: Spindle bearing replacement

Post by NP317 » Fri Jun 07, 2019 11:51 am

"There are exceptions, of course."
HARDINGE!!

Wish I had one.
~RN

jcfx
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Re: Spindle bearing replacement

Post by jcfx » Fri Jun 07, 2019 2:14 pm

John Hasler wrote:
Thu Jun 06, 2019 6:06 pm
You are measuring the vector sum of spindle runout, collet runout, and gauge pin runout. Because you are measuring 1" out part of what see may also be due to misalignment of the headstock and/or crookedness of the collet and/or pin.

Measure the spindle runout by placing the ball of the DTI probe directly on the inside of the spindle taper.
In measuring just the spindle runout I agree that the DTI probe would be in the spindle, but I think
what Wolfgang wanted is the runout of the work ( sum of spindle, collet and gauge pin or work ).
Cary Stewart wrote:
Thu Jun 06, 2019 7:47 pm
As for those Vermont X class pin gages you must read what the TIR, diameter tolerance and roundness tolerance are. There are very few home shop machinists that have the equipment and facility to verify that those pins are truly class X either + or - tolerance. I have a set of about 8 of those in various decimal sizes for both inch and metric diameters. If I recall the roundness of them is .000004 inches. The diameter is to .0000020 inches. Do I have the right number of 0s? To use this level of accuracy everything must be CLEAN.
Cary
.00004 diameter tolerance according to Vermont Gauges website, there doesn't seem to have a roundness tolerance listed.

John Hasler
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Re: Spindle bearing replacement

Post by John Hasler » Fri Jun 07, 2019 4:39 pm

jcfx wrote:
Fri Jun 07, 2019 2:14 pm
John Hasler wrote:
Thu Jun 06, 2019 6:06 pm
You are measuring the vector sum of spindle runout, collet runout, and gauge pin runout. Because you are measuring 1" out part of what see may also be due to misalignment of the headstock and/or crookedness of the collet and/or pin.

Measure the spindle runout by placing the ball of the DTI probe directly on the inside of the spindle taper.
In measuring just the spindle runout I agree that the DTI probe would be in the spindle, but I think
what Wolfgang wanted is the runout of the work ( sum of spindle, collet and gauge pin or work ).
Cary Stewart wrote:
Thu Jun 06, 2019 7:47 pm
As for those Vermont X class pin gages you must read what the TIR, diameter tolerance and roundness tolerance are. There are very few home shop machinists that have the equipment and facility to verify that those pins are truly class X either + or - tolerance. I have a set of about 8 of those in various decimal sizes for both inch and metric diameters. If I recall the roundness of them is .000004 inches. The diameter is to .0000020 inches. Do I have the right number of 0s? To use this level of accuracy everything must be CLEAN.
Cary
.00004 diameter tolerance according to Vermont Gauges website, there doesn't seem to have a roundness tolerance listed.
I thought he wanted to find out if his spindle bearings were damaged.

jcfx
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Re: Spindle bearing replacement

Post by jcfx » Fri Jun 07, 2019 5:17 pm

The gist I got was he wanted to see if someone with the same model lathe was getting the same runout
he was getting on his based on how he measured his.

Wolfgang
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Re: Spindle bearing replacement

Post by Wolfgang » Sat Jun 08, 2019 4:59 pm

jcfx wrote:
Fri Jun 07, 2019 5:17 pm
The gist I got was he wanted to see if someone with the same model lathe was getting the same runout
he was getting on his based on how he measured his.
Indeed, that's what I wanted to know. Next step will be to measure the TIR of the spindle nose collet taper itself, and then make a decision as to what class of bearings to get.

Here is a thought: If the class run-out tolerances are .0002" max. and .0004" max (P5 and P6 limits for the larger bearings respectively, what are the odds of getting bearings with run-outs of about half of the limits specified? I'm thinking here of the standard distribution of actual production run-outs, whereby the great majority of run-outs would fall into the middle of the tolerance band. w

armscor 1
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Re: Spindle bearing replacement

Post by armscor 1 » Sat Jun 08, 2019 5:22 pm

Recently replaced my spindle bearings on my 9" lathe.
Converted them from ACR ball bearings to tapered roller bearings, used bog standard garden variety Koyo bearings and no measurable runout.
I think all the bearings are made on the same machine and are graded to the different tolerances and stamped accordingly and you pay an arm and a leg for the higher tolerance bearing.
That's my take on it but I might be wrong.

John Hasler
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Re: Spindle bearing replacement

Post by John Hasler » Sat Jun 08, 2019 5:38 pm

Wolfgang writes:
Here is a thought: If the class run-out tolerances are .0002" max. and .0004" max (P5 and P6 limits for the larger bearings respectively, what are the odds of getting bearings with run-outs of about half of the limits specified? I'm thinking here of the standard distribution of actual production run-outs, whereby the great majority of run-outs would fall into the middle of the tolerance band.

They may be running a single, common production line for all grades and then classifying them.

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