Of spindle chatter and bearings...

[CapnDenny1]

I recently bought an Asian lathe of eBay. I bought an MX-210V. It has a thru spindle diameter of 1.4", and needed a finished size of 1.1".

But the lathe was just about useless because of excessive chatter. I asked my brother for help, but he couldn't it out. He is a machinist, but everything is CNC for his job, so.. I've watched videos and really struggled. Then one day I was looking for loose stuff, since the videos say that's one of the causes of chatter, and I tried to wiggle the 3 jaw chuck. Tony amazement it was loose as a goose. I could easily wiggle the work piece up and down by 0.100" or more!

So I determined the bearing at the chuck is an angled roller bearing. The bearing at the drive end is a deep groove ball bearing. That makes no sense? Shouldn't the drive side bearing also be a tapered roller bearing? In spite of that I took the spindle out and examined it. The drive side bearing with the deep groove ball bearings does not slide onto the shaft very easily. It's OK up to where it is supposed to sit and the spindle gets thicker and appears to have been polished. But it's just too big to go inside the bearing. I could probably drive it on, but my understanding is I use the spindle nut to pre-load the tapered roller bearing at the chuck end. But it has to pull the spindle thru the left bearing. If it binds up then it won't do a very good job of pre-loading the bearings.

I tried using some Emory paper, but it was slow going. So I went ahead and put it together and tightened up the nut. It took a lot of force, but eventually I was able to get it to tighten up, and I could not feel any up and down slop in the chuck end of the spindle. So put it back together and it was able to cut finally. I managed to make one of the 4 pieces I needed to make.

It worked until I got to the time I needed to perform a cutoff of the 1.25" aluminum bar. Then it started to chatter really bad again, and I could see the piece wobbling really bad. I checked the up and down movement and it was loose again?

It has two nuts on the end of the spindle to lock them. So I figured they just got loose again. So this time I used Permatex Blue threadlocker on the threads. So I got it all back together again. Went to the cutoff, and at first it was ok, but it started to chatter more and more, and then got really bad again. I checked the up and down motion, and it was loose.

The nuts were almost impossible to remove with the threadlocker on them? I had to hammer them off. And the thing is, there is no way the nuts just backed off.

So I have a new set 2 angled roller bearings, one for each end.

But what is going on?

Should I just use the hacksaw to cutoff?

Should I work on the shaft until the bearing can slide on the shaft?

I took the outer race out at the chuck end, and there was a bearing cover between the outer bearing race and the casting? It's like it was being used as a spacer.

So that is my story. I guess I will try to put the two new bearings in there. But Ild like to understand how the bearing can seem tight, then get some chatter, and it loosen up?

 

[Superburban]

Two thoughts. One like you are thinking, the nuts are loosing the assembly. The other, is when things heat up the bearing is expanding ever so slightly, and sliding a bit further on the shaft.

To test the first, I would mark a spot on the nut, and the shaft, with a dab of paint or something. Then test the lathe with something that will make it work a bit.

I'll search up info on that lathe, and see if I have any other ideas.

 

[addertooth]

Some bearings are press-fit onto the spindle shaft. If they are not seated all the way, as the spindle settles deeper it can create enough room to have some slap. The various videos on upgrading the 7X12 bearings go into this, which is why they suggest you carefully hone enough off the spindle O.D. for one of the bearings to be mobile. This prevents it from getting stuck on the spindle before getting fully seated.

 

[matthewsx]

Hello and welcome.

My first question is how long ago did you buy this lathe? It sounds like it never worked properly so if you just got it you may want to contact the seller and/or eBay.

We expect Chinese machine tools to be kits to a certain degree but yours sounds like it might be a lemon. There are others on here who might be able to help with something like this, also lots of youTube tutorials.

John

 

[CapnDenny1]

First off, I'd like to thank everyone for their replies. It looks like I found a good place to ask for help.

The lathe is about a month old. The ebay seller was responsive, and offered to send a new bearing, or $60 refund so I could just source the bearing locally. I already had a pair of tapered roller bearings on the way.

The bearings I ordered were 30209, or 45x85x21.5 tapered roller.

After I pulled the bearings both from the casting I could see the numbers. The chuck end was a 30209, so good guess on my part. I actually measured it. The drive end bearing was a 6209 RS, which is a 45x85x19 sealed deep groove ball bearing.

I don't think heating is an issue. But when doing cuts, especially doing a cut off, there is a ton of vibration. So I can see where it would do the impact hammer kind of thing, and be able to move the bearing, even on the tight shaft.

What is a good way to reduce the size of the shaft to allow it to move through the bearing on the drive side? If only I had a lathe!

I should probably check the chuck end bearing to make sure it is completely seated as well.

 

[C-Bag]

I had a similar problem with my 9x20 which going through posts methodically here I found out the cure. It was a multi solution as there was a problem with the crossslide gibs too. And the way the QCTP was mounted. Every thing helped get rid of chatter. But it was a long process of elimination.

Mine has tapered bearings on both ends. And from the factory they were both press fit on the spindle. Like you’ve deduced the bearing on the drive end needs to be a slip fit in order to set the preload properly. Since I didn’t have another lathe to take off the necessary aprox .0005 I made a rig to mount the spindle in my drill press and slowly and carefully filed and sanded until I got the proper slip fit. No more problem with adjustment changing. You might have to use a torch to loosen the Loctite. As you see, that’s not at all a good solution.

 

[addertooth]

CapnDenny1,
Pay attention to the jig that C-Bag has shown. Many like you (including me) only has one lathe. But, many DO have a drill press. This is a good way to spin the spindle with both ends supported, to get a more even honing. You don't need to hone the entire shaft, if you are CERTAIN you got the bearing closest to the chuck deeply seated onto the spindle (half-way will work nicely). And I do mean ALL they way down. It is only the bearing furthest from the spindle that needs to be able to move down the spindle with light friction. This way, preload can be set, and should be consistent. If you care considering adding a "spider" to your set up, it should be added when you are assembling it. This way, you aren't adjusting bearing pre-load twice.

 

[CapnDenny1]

I thought about using the drill press, but I thought, "That will never work!" But I hadn't considered supporting both ends. I also briefly thought of using the wood lathe? Maybe I could use a speed control to slow it down?

There is lots of slop elsewhere I know. And plan to work those issues too. But until I fix this problem they are very much secondary to the problem.

Thanks, it's encouraging to see others fix these issues. it helps also knowing I am on the right track.

I am an EE for 45 years, and worked on my own cars and motorcycles in my younger years. But this stuff is all a bit new to me. But that also makes it fun!

 

[addertooth]

I thought about using the drill press, but I thought, "That will never work!" But I hadn't considered supporting both ends. I also briefly thought of using the wood lathe? Maybe I could use a speed control to slow it down?

There is lots of slop elsewhere I know. And plan to work those issues too. But until I fix this problem they are very much secondary to the problem.

Thanks, it's encouraging to see others fix these issues. it helps also knowing I am on the right track.

I am an EE for 45 years, and worked on my own cars and motorcycles in my younger years. But this stuff is all a bit new to me. But that also makes it fun!

I started life as a Machinist, and over time migrated to EE Engineering work. So, understand your path. An understanding of Precision applies to many domains.

 

[C-Bag]

I also briefly thought of using the wood lathe? Maybe I could use a speed control to slow it down?

I would use that in a heart beat. Like one member's tag line says, "tools, not rules". Machining is all about correctly identifying the problem and finding a way to correct it.

There is lots of slop elsewhere I know. And plan to work those issues too. But until I fix this problem they are very much secondary to the problem.

I disagree. In my lathe's case the slop in the QCTP and crosslide were the beginning of the cure. And as I took care of them I could take bigger cuts and that's where the next domino fell. I actually started with my lathe bits as even though I was already using HSS I didn't have really good optic's to check my grinds. That's why I call it domino's because one thing led to another, to another etc. So proper leveling, alignment of head to bed, grinding angles, proper grinder, good optic's(found a stereo microscope on CL for $40!), then tool post, then crosslide, then headstock bearings and fit to the spindle and finally proper pre load. They are all crucial and without them all you can think you've not cured anything. It was a long process but it was totally worth it. And I learned a LOT.