Thread: Spindle play on ARM

Hi all,
New owner/user here in NZ looking for help.
I'm trying to sort out my spindle play. I've been using the machine ok for a couple of months, but the spindle play was bugging me and affecting facing and parting cuts.
I removed the spindle to check the main bearings. The chuck-side one looks like it has been replaced already at some point. It's a Japanese non-Timken, but with the correct code stamped on it. Both main bearings seem fine to me.
I can't get rid of the play with the take-up nut. It's fully tightened, even tapping it with a pin punch (oops, I didn't know better) but still is say about 1 or 2 mm play. Something very wrong, right?
Now, if I remove the big shim/bung/bushing thing under the take-up nut (am I correct that the roller bearing headstock has no fiber washer?) And do the take-up nut up against the headstock casting instead, that pulls the spindle snug, and all play is gone.
But I'd guess like that it's not preloading that bearing, is it? The bush/bung/shim thing would transfer the push from the take-up nut to the bearing race. But not if I've removed it.
Any thoughts why pulling against the bearing race won't snug my spindle, yet pulling against the headstock casting will?
Thanks in advance,
Eric

First image, so we know what we're dealing with, is the headstock of my AR (Sorry, not an ARM like the title said), with the backgear cover protection shrouds removed, the banjo and tumbler gone, the chuck off, and a little aluminium bar projecting out the threaded spout of the spindle.

image002.jpg


Second image, is later after i removed the spindle onto that projecting aluminium bar, which was held in the tailstock chuck, and once it was all loaded up, rested on the toolpost to support it. You can see the various bits on there (apart from the left hand roller bearing, which is still in the headstock). Left to right on that spindle are the pair of big hmm bushings which I think are to stop the oil leaking so fast out of the left hand spindle bearing. It's these parts that I'm currently most suspicious of.

image007.jpg

They're different diameters. In situ the left one projects out of the headstock casting, and it's what the take-up nut bears against:
image004.jpg

There it is there. With that bung in place the takeup nut does up tight against it, but I can still shift the entire spindle left-right-left-right at least a millimetre. I havent bothered to indicate it, it's obviously horrific. There's something wrong. My next step (these always occur to me overnight) is to go out and check just how many of the components of the stack are moving with the spindle when I do that. Is the right-hand bung (vis in pic 2) moving also?

Anyway, with the left-hand bung not there:
image003.jpg
and instead putting a large washer in place (not shown), I then do up the take-up nut effectively (due to the washer) against the headstock casting. Now, I would have thought that would be equivalent to doing it up against the bush/bung, which presses against the bearing race, transferring to the bearing hmm cone(?) and thence to the casting, but when I do it direct (via washer) to the casting, it pulls the spindle snug, removes play and I can't L-R-L-R it any more. The take-up nut then behaves as it should.

So my diagnosis is that something's wrong. I think I'd get these same symptoms if the left hand bung was coming up against a shelf on the spindle rather than against the bearing. But (see fig 2) the spindle appears to have no such shelf. Sure, it could be tinyscopic so that I wouldnt see it without really looking, but I reckon I've slid that bung along the spindle reasonably freely. (You can imagine I'm squeamish about getting the spindle in and out and in and out for all these trials and look-sees).

Now, the right-hand bung:
image006.jpg
Shown here sitting on top of the headstock casting, is much tighter on the spindle. I think that it's the bulk of the friction as I'm removing the spindle. It has a number of keyways in it - is that what's meant to be keyed to the spindle there? The spindle has a keyway too, but there was no key. No need for one either I would have thought, as it's so tight. At one point I suspected this bung was causing the dramas, so left it out during assembly. But when I did so, the takeup nut still wouldnt remove play unless the left-hand bung was removed. That is, the right-hand bung made no difference to the behaviour of the setup. I think it's in the clear.

So back to the left-hand bung. It seems to be blocked against something, so that pulling the spindle against it won't pull the spindle snug. Like it's blocked on the spindle. Either that or the bearing race is similarly prevented from sliding futher along the spindle. Or the bearing cone. I'm pretty sure the cone won't be doing the L-R-L-R shuffle, as it seemed too tight to easily remove.

In terms of what bits spin with the spindle, right? The cone should be stationary with the headstock, and the right hand bush is tight on the spindle, so rotates. That means there's rotation between the RH bush and the cone, right? The bearing rollers should rotate with the spindle, but presumably the race doesnt keep up with the rollers. It's bearing against the bush, which presumably rotates with the takeup nut on the spindle. So the race probably actually rotates about with the spindle, right? That rotation between the right hand bush and the bearing cone concerns me, I wonder if I'm wrong about what that RH bush bears against. Maybe it can reach through the cone, and also bears against the race? (Edit 4 march: yes, the right hand spacer is chamfered to reach inside the outer race and contacts the inner race, so turns with the spindle.)

My apologies for the dual posts on this topic. I thought I'd hit the wrong button on my first post and losten it to the ether, so wrote up another version of kind of the same thing, minus a few resolved confusions. I'm pretty sure now that the roller bearing setup doesnt need the inboard thrust bearing. I'd still like confirmation though about whether the "fibre washer" should be part of the stack set up on my machine. THe one that folks upgrade to needle roller bearing.

OK thanks again, wish me luck.

Eric

Right, I drove out the outer race, the cone-shaped bit, out of the headstock casting on the LHS there. I thought maybe there was some swarf or chip that had prevented it from seating properly. I've got it in the freezer, with the spindle. I've cleaned out the seat in the headstock and I've cleaned all the other bits, those spacers and whatnot. I'd eat my dinner off it now.

And then my buddy rang. And I've been asking him lots of questions and sending him the photos, so he's pretty much up with the play (sorry), and he suggested it's the absolute opposite of what I suspected. He thought maybe that outer race had been seated too deep, and that I might in fact need to shim that outer race out further! The genius! The man's a poet warrior!

Is that heard of? Shimming the roller bearing outer races apart slightly?

Thanks,
Eric

Do you have a sectioned drawing, like this one of a 260?
It might help figure out what should be there.
Any chance a spacer is missing, or a non-original wrong size part used?

Thanks Jordan, no I didn't have a diagram to work from. That's much appreciated. Yes I had wondered whether my complement of componentry was correct. Something missing, something wrongly sized maybe. My guess is that the roller 9 and the 260 are reasonably close, but there look to be a few key differences. I'm hoping someone might come up with a similar dimensioned drawing for the 9.

Sounds like a simple fix really, the keyed spacer on the left side that sits between the cone pulley and the take up nut will probably need a couple of thou taken off, if the bull gear is all the way home then that is going to be the problem, I had to do that with mine, there should be between 3 and 7 thou clearance between the spacer and the cone pulley.

Thanks Tinkerer, for that idea. I had tried assembling it entirely without that right hand spacer (which would be the most extreme thinning you could do), and it had no effect on my ability to tighten the spindle. I'll check though to see whether there's any clearance there.

Eric

Actually tinkerer, would you mind clarifying for me please, which spacer you were suggesting should be faced down? There are two between the cone pulley and the take-up nut. One either side of that roller bearing. Leaving out the left one and replacing it with a large washer means I can tighten the spindle properly. Leaving out the right hand one send to have no effect, the one time I tried it.
Eric

Oh, right, "clearance from the cone pulley". That's pretty unambiguous about which spacer you mean. OK.

Got it!! I got it!!!

And it wasnt shimming and it wasnt skimming, it was hammering!

The shimming the outer race forward to contact the rollers sort of made sense to me, but I couldnt see why the rollers wouldnt press back to contact the outer race. Why should I have to shim it forward?

So I reassembled it with a frozen-cold spindle (seemed to make no difference), and as I was seating each part I made sure it was well and truly home. I tappy-tapped the outer race home into the casting, measuring each quadrant to see which was still high, and needed more tappy-tap. Then the left-hand ball race: once the spindle was in place, I brought the tailstock up against it and wound it some pressure to hold it left-ward. The ballrace part wouldnt slide far up the spindle. It was real tight. THat's the bit that the take-up nut should be able to slide down the spindle, right? So, I felt like it was too tight for the take-up nut to shift. Instead I used a bullet of aluminium and a good japanese hammer, and tapped it home. Tappy tap, tappy tap. Bash bash. Wallop. I could test it by backing off the tailstock, and checking the play. Still a millimetre, more tappy tap, half a mil, tap tap, snug! On with the spacer, on with the take-up nut. The take-up nut had a tight spot in the thread at the place where it must have spent quite a bit of time with the play jiggling a burr on the threads maybe. Another tap to get it past that, and it snugged up against the spacer which was against the ballrace, and bingo! No play, headstock rotates, I'm happy.

Thanks for bearing (groan) with me, and watching this space (oof) while the drama played (uurgh) out.

Eric

Hi Eric, Guys,

I am making assumptions here, because I've not played with a Hercus lathe. Mines a Myford, similar but not the same.

I would have thought that the bearing that you describe should be a finger press fit on the spindle, since the threaded collar is the part that sets the preload on the spindle bearing to adjust the play, it has to be able to move.

I agree that there should not be any end float in the spindle.

Yes I think they're probably much the same machine in many regards. And yes I think that bearing should really move much more freely then it does in my spindle. Somehow something might be out of round or have a little scuff somewhere that stops it moving cleanly. For now though it seems all good.
Did I mention this lathe was once-upon-a-time rolled off a forklift? I guess it's possible that incident could have somehow affected the spindle precision. I don't think it or the headstock took any direct hits during that maneuver though. Mark Twain: "Luckily my face broke my fall". Bent cross slide screw and T handle, bent tailstock screw and smashed retainer nut and cracked casting, and broken countershaft bearing yoke. Nothing a bit of JB weld couldn't buff out.
Eric

Originally Posted by Erolgo

Yes I think they're probably much the same machine in many regards. And yes I think that bearing should really move much more freely then it does in my spindle. Somehow something might be out of round or have a little scuff somewhere that stops it moving cleanly. For now though it seems all good.

Yes I would agree. It would take very little to make the bearing a tight fit.

Did I mention this lathe was once-upon-a-time rolled off a forklift? I guess it's possible that incident could have somehow affected the spindle precision. I don't think it or the headstock took any direct hits during that maneuver though. Mark Twain: "Luckily my face broke my fall". Bent cross slide screw and T handle, bent tailstock screw and smashed retainer nut and cracked casting, and broken countershaft bearing yoke. Nothing a bit of JB weld couldn't buff out.
Eric

Ouch ! At least you have a runner now .