What is allowable play in Babbitt bearings on a lathe spindle?

Dr. Hillbilly · Dec 30, 2019

I have started working through the 1904 LeBlond I just acquired and observe .0015 play in the back bearing, and .0042 in the front. This seems extreme in the front, but what is acceptable?
My only experience with poured Babbitt is in my 1929 Model A, and those bearings are smaller in diameter, better lubricated, and running at much higher speed (but run at .0015 clearance).

Milland · Dec 30, 2019

Do some searching using the terms "babbitt spindle bearing clearance".

Babbitt Bearings & Oil Film Thickness? is a place to start, the link at the end of that thread is excellent for real engineering information (but likely more than you need).

I agree with you that the front clearance is too much.

Rob F. · Dec 31, 2019

Does it have any shims under the bearing cap? If not, maybe a good idea to put some in for next time.

enginebill · Dec 31, 2019

Do you have a 48" lathe or a 14" lathe. I think .001" clearance for a 14" lathe is good and go up from there.

johnoder · Dec 31, 2019

More important to me...

Turns freely by hand

Does not heat much at all at top speed

I guess that equates to as little as possible clearance

It is after all a precision machine tool, not a wheelbarrow

Dr. Hillbilly · Dec 31, 2019

Milland said:
Do some searching using the terms "babbitt spindle bearing clearance".

Babbitt Bearings & Oil Film Thickness? is a place to start, the link at the end of that thread is excellent for real engineering information (but likely more than you need).

I agree with you that the front clearance is too much.

Too much engineering information? That must be some sort of oxymoron!
I have done some design of hydrostatic and hydrodynamic bearings, but at the low rpm and low flow of oil in this spindle I cannot count on the generation of a proper oil wedge.
.0005" per in. of shaft diameter sounds about right. I will pull the bearing caps and see what I have... Perhaps I get lucky and the bearing is split and shimmed, and I can just adjust the shim stack.

And it is a 17" lathe with a 3" shaft. So scaling from the 14" lathe gets me close to the .0015" resulting from the .0005" per inch guide.

gbent · Dec 31, 2019

Are you having problems with the quality of work the lathe is producing? If its not broke don't fix it.

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What is allowable play in Babbitt bearings on a lathe spindle?

Dr. Hillbilly

Aluminum

Milland

Diamond

Rob F.

Diamond

enginebill

Stainless

johnoder

Diamond

Dr. Hillbilly

Aluminum

gbent

Diamond

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