New Member with a question

Robert Shimko · Feb 5, 2020

I recently acquired a 1939 South Bend 9" workshop lathe (415YA) and need to know if the spindle needs some work. This lathe appears to have been used little, and not at all for the past 30 years.
My question is how much spindle runout is acceptable? I first put my dial indicator on a piece of 1/4" drill blank in my small three jawed chuck and got several thousandths runout (about .004/.005).
Then, because I had my indicator clamped to the tool holder, I locked down my saddle and the runout went down to about .0015".
So I put on the smaller three jawed chuck and had similar runout. Finally I put a 1/4 collet in the spindle and used the collet draw wheel and had the same amount of runout (.0015")

So I ask the collective group, Is this acceptable runout, or should I rebuild the spindle?

Thanks for any help. Pictures attached.

USNmechanic · Feb 5, 2020

From your test descriptions, it sounds like you’re compounding the runout of your spindle and chuck during your test. Even new 3-jaw chucks won’t grip perfectly concentric with the axis of the spindle. Have you measured the register of the spindle without a chuck installed?

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TDegenhart · Feb 5, 2020

I don't quite know what you mean by clamping the saddle. Take the chucks off the spindle and measure the runout directly. The numbers you listed for 3 jaw chucks and the old tooling is not unusual.

Tom

SLK001 · Feb 5, 2020

To check the spindle, you need to perform a "lift" test, with the power off. And, you don't "rebuild the spindle" - all you can do is adjust the bearing spacing.

iwananew10K · Feb 5, 2020

yes, check the spindle AT the spindle. no chucks or anything.

can be a little tight but get that indictor on the unthreaded portion of the spindle.

seeing as plain drill rod is NOT straight or concentric, i agree, most of what you are seeing with a collet is likely stacked errors...collet not quite perfect, drill rod not either....it all adds up.

Robert Shimko · Feb 6, 2020

Thanks for all of your answers and suggestions.
First, I was using a hardened drill blank which would have more than likely been run through a centerless grinder.
When I worked in a machine shop as a toolmaker, we knew these to be straight and round. Of course you would check them first on the surface plate if used on antyhing critical.
Secondly, When I mentioned clamping the saddle, I meant that I tightend the lock screw on the saddle.
I will remove all of the chucks, collets etc. and check the spindle directly on the unthreaded portion and see what I get. I will provide pictures of my set up to remove the confusion.
Again, thank yo all for you help and suggestions.

Mike1974 · Feb 6, 2020

To directly answer your question, .0015" on an old machine ain't tooo bad. If you are going to be doing alot of 'flip' work (turn one end, flip 180 and turn the other end) you might want to get a 4 jaw so you can dial in your parts to what you need as far as max runout. From there it is just making sure your cutting setup is rigid (as possible) and there isn't a lot of slop in the machine itself and you should be fine.

Robert Shimko · Feb 6, 2020

Thanks Mike,
I was hoping that this was normal runout for this machine.
I do have a four jawed chuck that I can use, and I have Hardinge quick change tool holder.
I had to make the actual tool holder because That didn't come with the base.

As you can see, I didn't have any steel, so I made it from aluminum. Hope it holds up for a little while.

Robert Shimko · Feb 6, 2020

After doing what you guys suggested, I see that my indicator reads about 2 to 3 ten thousandths of runout while revolving the spindle by hand.
When I take the slack out of the drive belt, I can see the indicator jump about a half thousandth, but it still only mooves a couple of tenths when rotated. I will call this spindle plenty good.

USNmechanic · Feb 6, 2020

Nice! Have you checked the bearing clearances as well?

From the pictures, it looks like you’ve gotten yourself a very nice lathe!

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SLK001 · Feb 6, 2020

The spindle floats on a layer of oil. Put the lathe in low back gear and let it run for a couple of seconds before you check the runout.

Robert Shimko · Feb 6, 2020

Edited for double post

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