Of spindle chatter and bearings...

[CapnDenny1]

I know there are other issues. But when the spindle bearing was tight, it worked pretty well. Nice controlled cuts, decent finish, etc. But then the bearings would move, and it just went to heck.

If I solve this one, then it will be worth it to make the other issues better. One step at a time. Otherwise it's too big a problem.

 

[Mitch Alsup]

It seems to me that what you need to do is to insert the bearings and TQ down the lash nuts.
Do a few turning passes until chatter shows up, the TQ the nuts down again,
Do the above 4-5 times until the bearings no longer seat themselves farther into their housings.

Then let the machine run at 75% rated RPMs for 10 minutes and check bearing temperatures by hand. Too hot, back the nut off by 5º, not even warm, add 5º to the nut.

 

[Lo-Fi]

Swapping bearings

It seems to me that what you need to do is to insert the bearings and TQ down the lash nuts.
Do a few turning passes until chatter shows up, the TQ the nuts down again,
Do the above 4-5 times until the bearings no longer seat themselves farther into their housings.

Then let the machine run at 75% rated RPMs for 10 minutes and check bearing temperatures by hand. Too hot, back the nut off by 5º, not even warm, add 5º to the nut.

Get some quality bearings in it if you haven't already, then follow the above. Also, warming the bearing inner race up slightly will help you seat it initially. Only 100deg or so, nothing crazy, and be quick when positioning it.

 

[CapnDenny1]

Thanks again, but... (shows how much I have to learn.)

I was under the impression that once you set the pre-load, you were done. I've never seen anybody talk about having to re-tighten, and re-tighten?

And as far as heating the bearing. I also read the suggestion of putting the spindle in the freezer overnight. I understand that the colder part is smaller and the hotter part is larger. But, I need at least the drive end to be free to move don't I? I guess if it is adjusted correctly as I thought it would be, then it doesn't matter how you got it there, as long as the bearings are in the right place.

I think that makes perfect sense for the outer baring races. To put those in the freezer or even just the fridge. But both of those move pretty easily. It's the one on the shaft that is too tight.

On the other hand, if I make it too loose by reducing the shaft, then no amount of tightening can fix that.

OK, too many variables!

 

[Lo-Fi]

A good interference fit is maybe a thou or two at the sizes we're looking at here. Steel expands roughly 1 thou per inch per 100F. Heat the shaft, cool the spindle. Either way you're making life much easier for yourself.

What's probably happening in your case is the bearing race is a rather tight and you're struggling to shift it without some serious force in the nut, which leads to not getting decent preload. Keep at it, you'll get a feel for it.

This will give you a good idea, much as it's a very different lathe:

Notice he had trouble parting until it was tightened up too, even on a large lathe!

 

[C-Bag]

Being a mechanic by trade and dealing with proper clearances once I got how this thing was supposed to work and getting coherent info I knew what I was supposed to do. I have many different kinds of pullers and an arbor press. The hard part was getting the slip fit on the spindle. It should be noted just like when you are turning a piece of metal to size you need to take the temp of the spindle into account. What won't fit when warm will be sloppy the same temp as the bearing.

I know this is a lot to take in but ignorance is not bliss when dealing with precision machinery. That's why I do a LOT of studying before I start tearing something apart. Once you have all the info you can also have a better chance of avoiding disaster.

There is no way the drive side bearing can be adjusted properly when it's an interference fit. Many of us have been there and know this is the product of bad QC at the factory.

 

[CapnDenny1]

I finally managed to get the new bearings in. I first had to undo my previous attempts. I used Locktite blue and it got all over the threads and it hardened. I used a heatgun and a pick to clean up the threads.

When I pulled the chuck side bearing race out of the headstock, I found a crude spacer in there taking up space. It didn't look very precise, so I just left it out when I put it back together. I think it was a bearing cover plate they were using as a spacer.

I elected to not doing any work on the spindle. It took some work getting the old bearings off, but using my digital calipers I decided the old bearings were tighter than the new ones. I drove the chuck side bearing past the other bearings high spot just a little at a time on each side. It went on easier than the old ones came off to be sure. I just used the threads on the spindle to pull the drive side bearing in, using the old ball bearing as a spacer. It worked.

I was able to get it to tighten up just fine so far. I ran the lathe at top speed for a minute or so, and it seemed OK. I ran out of time so I didn't do any machining yet. I decided to quit while I was ahead too.

I am afraid to try and do a cut off. I have a couple parts I need to make. I almost want to make those first because I need those parts ASAP. Then I can experiment with the cut off again.

I noticed the bearing seat for the outer bearing race, in the casting of the headstock, has some gouges or creases. I guess they are voids in the casting. I am afraid that perhaps the casting is cracked at those points. Perhaps that is the root cause of the creepage in the bearings? It seems like if you were making a tool, and your machining uncovered a void in the casting, in about the most important spot in the casting, you would reject that casting. I guess there's nothing like a quality tool. And that's exactly what I have. Nothing like a quality tool! I guess if I wanted a quality lathe, I should have bought one?

Well, wish me luck. I think I'm gonna need it.

 

[matthewsx]

Run it and see how it goes, if you're past the time to return it then you have what you have.

That's why I asked about how long you had it in my earlier post. What we've seen time and again on the forum is people buy these machines off eBay and once they get into them it's clear that they're factory seconds (or thirds). I suspect that the foundries supply lots of different "manufacturers" and when one sends back a reject instead of melting it back down they just sell it to someone else.
That's why so many on here advise buying through Precision Matthews or Grizzly, they tend to do quality control and are available to provide support when you need it.

The "shim" on your headstock bearing is a dead give-away that whoever was putting it together knew something was wrong. No, they don't stop and put a big "reject" sticker on them since China is a long way from us and they know many of these tools will never even get used. Typical eBay seller tactic to just offer a small "refund" and stall until your time runs out.

IMHO, if you will be using a lathe for projects in the future it's worth getting a good one. Doesn't have to be the biggest most expensive thing out there but the frustration of dealing with tools which were never suitable for the job isn't worth it to me.

Good luck whatever you end up doing, at least now you have a much better understanding of what to expect and how to inspect your next tool purchase.

John

 

[C-Bag]

Perhaps that is the root cause of the creepage in the bearings?

I would bet not, big time. You get to go however you want but sooner or later the spindle will have to be addressed. Because just as soon as you get it hot right in the middle of some job or afterwards when you go to use it again, it will be loose again. The original Emco these lathes are copied from didn't have the drive side spindle bearing a press fit, it was a slip fit.

 

[CapnDenny1]

Well I got it going. It seems to work ok. I was able to finish cutting off the piece I was doing when it messed up before. I then finished the drilling I needed to do and started on the 4th of 4 parts I needed to make.

On this last part it started to chatter again, so I was worried, but I didn't have the quick change handle locked down.

So far so good.

Once I get this last part done, I will start to work on adjusting the other parts, removing the slop in the other parts. The tailstock is not even close to being aligned with the head. There is an adjustment for horizontal, but not vertically.