# Timken Bearing fit question



## Abear (Apr 15, 2018)

I'm in the middle of swapping my babbit headstock with a timken headstock (10A-2B).  The timken bearings are very tight fit on the spindle.  The spindle came with the main bearing (closest to the bull gear) already installed.  When doing dry fit assembly, the bearing on the opposite side will only slip on over the threads, once they get to the smooth part of the spindle, they stop.  Should the bearings be press fitted?  I'm cautious to apply force or slight tapping with mallet, I need to be able to remove them for the actual install in the headstock.  All other components, gears, pulleys, and collars easily slip into place without force.

appreciate any advise...
thanks,
Jude


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## Moderatemixed (Apr 15, 2018)

I’ve rebuilt several head stocks and never had to press the bearing on the left. The bearing on the right is pressed on. For that reason I have not removed the bearing on the right (nearest the spindle nose, threaded end). Fortunately my bearings have been in good shape and have not required replacement. When putting it all back together, everything is a slip fit, or on occasion a tap or two, but never as you describe.


Sent from my iPad using Tapatalk


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## benmychree (Apr 15, 2018)

Perhaps you should measure the mating parts and see what sort of fit there is, and also check to see if there are any burrs that are making it difficult to assemble.  On my lathe (not like yours, the rear spindle bearing does require a slight press to assemble, I'd think that should be about metal to metal, that is they should measure the same size.  On a lathe, having a free sliding fit for the bearing inner race would allow radial  movement that would lead to inaccuracy of the spindle's running.


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## tertiaryjim (Apr 15, 2018)

Suggest you measure the bearing bore and fit. Probably shouldn't have more than 0.0002" interference but I would think 0.00005 would be best.
If its in that range you can heat the bearing in a oven to 120deg and it will slip on. 100deg for a very light press fit.
I always rub anti-sieze on shaft and bore but it has to be so thin that it's almost invisable.
Edit: I should have said 120 or 100deg above ambient temperature. Big difference.


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## markba633csi (Apr 15, 2018)

As John mentioned the left bearing should be a light interference fit but it may require you to put together a threaded rod and spacer tool to
pull it together.  That would be preferable to hammering it in. Use oil too.
Mark


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## Rooster (Apr 16, 2018)

Greetings, i have a Atlas 618 which i installed 2 new bearings on. Like Mark said, threaded rod with a spacer tube was necessary to get the left bearing on.


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## wa5cab (Apr 16, 2018)

While it is of course possible that the people who didn't have to press the left bearing cone on just didn't mention it, everyone until this thread who has commented on the left cone fit has said that it was tight.  This includes posts both here and on the Atlas-Craftsman group formerly on Yahoo and now on groups.io.  And yes, it does make determining where the zero end-float point is more difficult.


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## Kernbigo (Apr 16, 2018)

The left bearing has to be a slip fit or
 you will not be able to set the bearing clearance.


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## woodchucker (Apr 16, 2018)

In general I have used a hot plate to heat bearings so they expand to fit on shafts. I am not talking spindles, just in general on tight fits.


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## cdhknives (Apr 16, 2018)

I know when I changed my bearings I thought it was all tight until strange things started showing up in my cuts...and I had a good 2 turns of the nut worth in looseness back...so recheck after running for a while no matter what.


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## Abear (Apr 16, 2018)

Thank you all for the feedback. I’ll measure the spindle and the bearings and report back what I find. I had considered heating the bearings but wasn’t sure of how much to heat, so thank you tertairyjim for that info.  I’m eager to complete the assembly, maybe tonight after the kids karate classes.  

Thanks again
Jude


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## BtoVin83 (Apr 16, 2018)

In a single cup installation Timkens can stand a lot of press fit on both cone and cup because the final take up is the end play, what they do not tolerate is out of round


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## wa5cab (Apr 16, 2018)

As I wrote earlier, although one would think from the way in which the end float is adjusted that the cone is going to be at most a light push fit on the spindle, any number of reports indicate that isn't always the case.  I would make a puller from a length of 5/8" threaded rod (UNF if you can find it), a length of structural tubing with ID just slightly larger than the left end of the spindle, a shoulder washer to fit the tubing and one to fit the right end of the spindle. and some coupling (long pattern) nuts.  Or put the cone in something like a roasting bag and immerse it in boiling water for 15 or 20 minutes.  Carry the pan with the bearing to the lathe, take the bearing out of the water and out of the bag with an oven mitt and slide it onto the spindle and hold it and the spindle together until it cools off and locks.  Load the spacer, gear and threaded collar on the spindle.  Use a dial indicator to check end float, tightening the collar a tooth at a time until it goes to zero.  Then two more teeth for preload and tighten the set screws.


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## Kernbigo (Apr 16, 2018)

I rebuilt high speed spindles and also have rebuilt the spindle you are referring to with a press fit on the rear bearing you won't be able to adjust the spindle end play. Tha t rear bearing has to be a push fit in order to adjust.


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## Abear (Apr 16, 2018)

I managed to measure the bearing and the spindle tonight.  The bearing was 1.2450 and the spindle was 1.2490.  I heated the bearing and was able to get everything put together.  The bearing was a tight fit, I was able to pull it on with a threaded rod and spacer tool.  Thanks for the help...


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## Rooster (Apr 17, 2018)

Glad you made out. That's one fine looking head-stock.


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## MozamPete (Apr 17, 2018)

And you remembered to put the belt on first - Win Win. Looks good.


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## WCraig (Oct 12, 2018)

markba633csi said:


> As John mentioned the left bearing should be a light interference fit but it may require you to put together a threaded rod and spacer tool to
> pull it together.  That would be preferable to hammering it in. Use oil too.



I know this is an old thread, but I wanted to say thanks!  I've been struggling with the same tight (REALLY tight) fit on my Atlas 618.  I was devising a way to use an F-clamp over the top of the headstock but a threaded rod is just so much simpler and easier to align.  

I had tried heating the bearing using the old light bulb trick.  It was way too hot to hold and yet stopped moving about 3/8" from home.  I think the heat migrates quickly from the bearing to the spindle and there is no longer any clearance.

Since the process is anything but easy, I've decided to replace the bull gear while I'm in there.  I _could_ make the old one work but I don't want to have to do this again in my lifetime!

Thanks again.

Craig


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## wa5cab (Oct 13, 2018)

The threaded rod method for reinstalling the spindle bearings should if possible be used up to the point where you have reduced the spindle end float exactly to zero (as measured with a dial indicator).  Then follow the instructions in the Atlas Technical Bulletin on the Atlas 06 612...  by installing the threaded collar until tight and then advancing it by 1/16th of a turn or two teeth of the 32T spindle gear.  This preloads the spindle bearings by a little more than 0.002" and ensures that the bearings do not go loose when the spindle length grows slightly as it warms up.


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## WCraig (Oct 13, 2018)

I haven't seen yet how to measure "spindle end float".  Could someone point me to a write-up or summarize?  I do have a couple of dial indicators.  Thanks,

Craig


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## wa5cab (Oct 14, 2018)

"End Float", usually measured in thousandths of an inch, means axial movement of a shaft of some sort.  Probably the most convenient way to measure the spindle end float is to mount a dial indicator to your compound slide or QCTP at an elevation such that you can advance the carriage and bring the rod sticking out of the indicator to bear on the right end of the spindle.  Move the carriage out of the way. Tighten either the threaded collar or the nut on the threaded rod until you think that you are close to zero end float.  Then bring the indicator to bear on the right end of the spindle and while pushing the spindle toward the tailstock, zero the indicator.  Push and hold the spindle away from the tailstock and any movement of the indicator will be the end float.  Reduce the end float to zero by whatever method you are using and then tighten the collar 2 teeth of the spindle gear.  Then check that the spindle is still free to turn but with a slight drag.  This should all be done with all components at room temperature (~70°F).  When satisfied with the preload, check and confirm that the brass or lead pellet is still present in the tapped hole(s) in the collar, insert and tighten the set screw(s).  And finish reassembling the headstock.


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## oldscouser (Oct 30, 2018)

Hello Abear. It looks like the interference fit of the inner race on the shaft is suspect.  My reading of Fitting Practice Tables for taper roller bearings (both FAG and Timken) is that for an inner race of between 30mm to 50mm diameter the interference should be between 4 tenths and 15 tenths of a thou. An interference fit of 40 tenths of a thou seems way too high.  You could check your bearing bore diameter against the published tolerances for tapered roller bearing in the catalogues (https://bit.ly/2Jsd3GG) and then work out what the shaft diameter should be.


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## wa5cab (Oct 30, 2018)

Abear,

According to the Timken catalog that Ian gave the URL to and the copy of it that I already had on my local machine, the bore of the inner race of the Timken 14125A both Class 2 and Class 3 should be between 1.2500" and 1.2505".  The unused example that I have here agrees with that.  As best I can tell, it is bang on 1.2500".

However, if you are confident in the bearing preload applied, I wouldn't take it back apart.  But just finish putting it together and use it.


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## mattthemuppet2 (Oct 31, 2018)

no need to press on the left bearing on my 618, it's a tight slip fit but moves with some drag on the spindle.


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## oldscouser (Nov 1, 2018)

Hello again Abear. Robert mentioned that the bore of the inner race of the correct taper roller bearing is 1.250, -0.0 +0.0005.  And you have measured your shaft diameter at 1.2490.  In which case the inner race should be a nice slide fit, but it isn't.  Sooo, two questions spring to mind: is the TRB you are using the correct one and is the shaft diameter truly 1.2490?


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