Lead screw bearing stack on mini lathe

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kjkrum
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Lead screw bearing stack on mini lathe

Post by kjkrum »

Hello, all! I'm new here, so I hope this is the right place to ask.

My new mini lathe arrived covered in grit and grime, so I took it apart to clean it. I did a pretty good job of bagging and labeling everything, but missed one detail.

The tailstock end of the lead screw passes through a block that's screwed to the bed. There are thrust bearings on both sides of the block, each consisting of a set of ball bearings sandwiched between two races. On the tailstock side, the bearing is compressed by a threaded cap on the end of the lead screw. On the headstock side, the bearing is compressed by a short tapered section of the lead screw.

Here's what I forgot to note: there's an extra bearing race that has to be inserted somewhere in the stack in order to compress both bearings at the same time. Which side I put it on shifts the lead screw slightly one way or the other. Does it matter? Or, what should I look for to determine whether it matters? Should my main concern be making the change gears line up?
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NP317
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Re: Lead screw bearing stack on mini lathe

Post by NP317 »

Welcome kjkrum.
Your manual for the lathe should have a parts diagram that shows that assembly area.
What lathe and model do you have?
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John Hasler
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Re: Lead screw bearing stack on mini lathe

Post by John Hasler »

> Should my main concern be making the change gears line up?

That's what I would do.
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Steggy
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Re: Lead screw bearing stack on mini lathe

Post by Steggy »

kjkrum wrote: Sun Apr 04, 2021 5:10 pmShould my main concern be making the change gears line up?
Yes. BTW, be gentle with how much you preload the bearings.
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rmac
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Re: Lead screw bearing stack on mini lathe

Post by rmac »

Welcome kjkrum. This is a great forum for all kinds of questions! In case you're not aware of it, there's also a group that's specifically oriented towards mini lathe users. Look for it here:

https://groups.io/g/7x12MiniLathe

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kjkrum
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Re: Lead screw bearing stack on mini lathe

Post by kjkrum »

NP317 wrote: Sun Apr 04, 2021 6:20 pm Welcome kjkrum.
Your manual for the lathe should have a parts diagram that shows that assembly area.
What lathe and model do you have?
It's labeled MX-180V. It seems to be very similar to the Grizzly G0768. Neither owner's manual shows the extra part in the bearing stack. Maybe my lead screw wasn't quite manufactured to spec.
pete
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Re: Lead screw bearing stack on mini lathe

Post by pete »

Yes as others have said concentrate on having the gear teeth line up. The other end of the lead screw is only a bearing support. Ideally and with two thrust bearings there should be a total of 4 hardened and ground washers or races for the bearings to run against. When you say bearing race do you mean you have the exact same thing with a total of 5 or is one a sleeve with a different shape? Pictures of the parts would help. It's not impossible if you have a total of 5 that are all the same there was a factory mistake drilling the hole locations for what the Grizzly manual calls the lead screw bracket, part no. 423 and they simply used another washer as a spacer. That's still only a guess though. And it's doubtful they'd custom grind that washer to exactly match the first locations errors. So the gear tooth alignment still may not be as good as it should be. But arranging those races for the best gear tooth alignment would be what I'd do. I'd also accurately measure each one of the races for thickness. A dial or digital calipers measurements would be good enough. Not all thrust bearings have or use the same washer or race thickness on each side of the bearing. Afaik the thinner race always goes to the inside, or in your case in that bracket where there should be a counter bored face to support the face of each race. If there's different race thicknesses that also could be important in how there arranged.
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Bill Shields
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Re: Lead screw bearing stack on mini lathe

Post by Bill Shields »

is there a thrust bearing at the OTHER END of the lead screw? => gear end?
Too many things going on to bother listing them.
John Hasler
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Re: Lead screw bearing stack on mini lathe

Post by John Hasler »

Bill Shields wrote: Thu Apr 08, 2021 3:48 pm is there a thrust bearing at the OTHER END of the lead screw? => gear end?
Shouldn't be.
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Bill Shields
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Re: Lead screw bearing stack on mini lathe

Post by Bill Shields »

Not what I asked.. I asked IF there is one.

Loading of the bearings on the free end can be determined by what is on the other end.
Too many things going on to bother listing them.
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Re: Lead screw bearing stack on mini lathe

Post by whateg0 »

If the gears don't line up right regardless of the "extra's" placement, I'd make some new washers (shims) to get it like up. It just so happens a lathe call be used for stuff like that! 😉
kjkrum
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Re: Lead screw bearing stack on mini lathe

Post by kjkrum »

pete wrote: Wed Apr 07, 2021 1:24 pmWhen you say bearing race do you mean you have the exact same thing with a total of 5 or is one a sleeve with a different shape? Pictures of the parts would help. It's not impossible if you have a total of 5 that are all the same there was a factory mistake drilling the hole locations for what the Grizzly manual calls the lead screw bracket, part no. 423 and they simply used another washer as a spacer.
That's exactly what I mean, 5 visually identical steel races. I hadn't thought to measure their thicknesses, so thanks for that suggestion.
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