Thread: Lathe Spindle Bearing Adjustment

Hi All

After about 35 happy years with my lathe it has come time to change my drive belt. This involves taking my spindle out - no real issue with this.

When I go to reassemble it I would like some advice from you guys about adjusting the spindle bearings please.

The spindle is supported by tapered roller bearings and my question is about how to adjust them when I put it back together.

Should there be a small clearance or should it be preloaded? Of course I want the best for precision work and not to damage my bearings.

So whats the opinions- small clearance and how much or preloaded and how much?

Thanks in advance.

Steve

Hi Steve,

First of all I know almost nil about adjusting lathe bearings.

What I am sure of, is that respondents to your question will find it easier to answer if you can provide the details. The brand, model and swing dimension of your lathe.

I suspect just one adjustment dimension recommendation would not be universal to all lathes.

Grahame

You could buy link belt to save pulling the machine apart, I've heard good reports from it.

As for bearings if they are taper roller, nip them up, run the lathe and keep an eye on there temperature.
They should run warm, but you should be able to place your hand on them and not be uncomfortably hot.

I have a similarly aged lathe and my drive motor is mounted on a tilting platform. Levering up the edge of the platform takes all the tension out of the belts, 2 in my case, so I didn't need to remove any shafts / spindle when I replaced the belts. Might your lathe have a similar motor mount?

Charles

A lot of the answer to this question also comes down to how the bearings are lubricated, oil bath or pressure lube of greased for life will make a difference. But usually with taper rollers there is preloaded. Like Dave said, run warm but not hot.

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Originally Posted by caskwarrior

A lot of the answer to this question also comes down to how the bearings are lubricated, oil bath or pressure lube of greased for life will make a difference. But usually with taper rollers there is preloaded. Like Dave said, run warm but not hot.

Sent from my SM-G973F using Tapatalk

When I replaced my mill bearings years ago I searched the subject to death looking for a technical way to do preload taper roller bearing properly, and all came down to check the temperature, lol

I did buy a cheap digital inferred temperature tester to do it though, to take out any guess work.

Yes definately pre-load the bearings . I've got a Sheraton AR and a Premo both with TRB spindle. I was using a heavy wheel bearing grease but found this was too much of a drag on the motor, effecting the spindle speeds . Oil isn't good either as it just runs out all over the place . A good compromise is a thin grease . Penrite used to make steering box lube , a semi fluid lubricant/ I ended up using the average grease from the hardware store and just give a small shot of oil down the hole now and then to mix with the grease.

To adjust a preload to a manufactures spec you need a specified certain diameter to wrap a secured length of string around, the other end is attached to a weight measuring device (in the old days it was fish weighing scales). As you pull the scales the string rotates the the shaft and you note the measurement on the scales that was required to rotate the shaft and then adjust the bearing preload up or down until you get the correct measurement on the scale.

What do you do if you have no spec's?

My punt would be to put an indicator against the chuck and adjust the bearings until the spindle just has no end float, run the lathe and take a couple of facing cuts on something and then recheck for end float, if it has some re-adjust and repeat the procedure until you are happy that there is no end float, that is all you want, no end float.
If you have them a bit tight and the bearings get warm that heat may transfer to the shaft and when it gets warm it might grow that little bit longer and make the preload even tighter.
I did say might, if your surface finish seems to have suffered then nip them up a bee's d1ck more....

Just something to keep in mind if they are greased bearings - don't pack them FULL of grease.
I think the recommendation is something like 20% of the cavity between the rollers should be filled, but I can't recall where I got that figure from. If you pack them solid they will run hot regardless of the preload, plus you'll likely end up with grease everywhere.

Steve

If you are happy with the state of the spindle and bearings as is then I would leave well enough alone and go with a link belt, I did mine that way - purchased a B section belt from the UK via ebay (I think hendersonbearings) cost including postage was around $70, for some reason local cost is way more and not even in the ball park compared to overseas cost. I noticed smoother running.

For what it's worth. My lathe is an old flat belt thing. I 'laced' an automotive poly v belt (or 'serpentine'). Way more grip, less slip when oil. You get a belt longer than you need and cut it down. I laced it with lockwire. I even did a crap job at it and it is still going strong a few years later.

Originally Posted by StrayAlien

For what it's worth. My lathe is an old flat belt thing. I 'laced' an automotive poly v belt (or 'serpentine'). Way more grip, less slip when oil. You get a belt longer than you need and cut it down. I laced it with lockwire. I even did a crap job at it and it is still going strong a few years later.

Good idea Stray, I wonder if there is a flat belt clip that would work on a poly belt?

"pictures wanted". Okay, this might be embarrassing! The OP was about spindle bearings, but in the spirit of "you may not need to" here is a breakdown. The serpentine belt usage was one of those things I read about and gave a go. I hacked it together and it just work so well I've left it as is. Ugly though.

I got a belt, cut it to size, realised I had got it wrong, so patched a piece in.

It is 'laced' with stainless lockwire. The eyelets are from a small belt eyelet kit from spotlight store craft section.

On the underside (the 'v' side) I've cut away a small amount of rubber to permit the wire to be tucked away-ish. The belt is nearly silent and has no tick tick tick as it goes around.

My lathe cannot accept an endless belt and it must be joined in some way. Leather slipped, green fabricy thing with clip went tick tick tick and annoyed the hell out of me. This gives a huge amount of grip and is silent.

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You may not need the eyelets. The serpentine on the back of the surface grinder is done similarly but with no eyelets and is doing fine.

IMG_20200816_182607.jpg

Greg.

It works and that's all that matters

Hi Guys,

Apparently you can still buy "Alligator Clips" originally used for joining the ends of flat leather belts. They come in long lengths that you just cut off what you need and a wire or fibre pin pushed through the end to join them. Though I do remember some joins done with them did click as the joint hit the pulley.

https://duckduckgo.com/?q=Belt+joint...ages&ia=images