Loose or bad headstock bearings.

[DPittman]

Have a look at the photo and hopefully you can see the chatter marks increase as I get towards the headstock. I have the other end supported by a small live center in the tailstock. My first suspicion is loose spindle bearings but last I had checked there was no obvious sign of that. I will check again after this job but thought the picture might be helpful to others whatever the problem may be.
Any suggestions or tips are always welcome.

Edit I forgot to mention the turning g was done under power carriage feed so travel speed (and depth) was consistent.

 

[thestelster]

Have a look at the photo and hopefully you can see the chatter marks increase as I get towards the headstock. I have the other end supported by a small live center in the tailstock. My first suspicion is loose spindle bearings but last I had checked there was no obvious sign of that. I will check again after this job but thought the picture might be helpful to others whatever the problem may be.
Any suggestions or tips are always welcome.

Edit I forgot to mention the turning g was done under power carriage feed so travel speed (and depth) was consistent.
View attachment 30250

Inspect the edge of your insert. Around mid point on your piece is a mark, and then the chatter got worse.

 

[Retiredmachineman]

increase feed rate and use a stay bottle with coolant if no coolant pump

 

[Susquatch]

I agree with @thestelster.

Also, your chips are those nasty tight long curlies. Those are notorious for getting caught under the tool and wreaking havoc! Check the data on your insert regarding speed, DOC, and Feed Rate for better chip breaking performance.

I can't yet recognize inserts by material. Check to make sure it is compatable with the material you are cutting.

If all else fails, try HSS......!

I'm not suspicious of your bearings just yet.

 

[Former Member]

Your problem may be self induced.

Since one end is on a center and the other is not you may have a bit of bend moment at the chuck end, ideally you should run between centers with a dog.

If thats not possible, loosen the chuck a little and retighten lightly, again a just a touch of pressure on the center.

 

[Susquatch]

Your problem may be self induced.

Since one end is on a center and the other is not you may have a bit of bend moment at the chuck end, ideally you should run between centers with a dog.

If thats not possible, loosen the chuck a little and retighten lightly, again a just a touch of pressure on the center.

This would be a first for me. In 40 years of using a lathe I've always avoided the dog and its never bitten me.

But I am always open to learning something new. Gunna keep an eye open for this one to piss on my bushes.

 

[DPittman]

Inspect the edge of your insert. Around mid point on your piece is a mark, and then the chatter got worse.

Interesting. I seemed to get this chatter repeatedly near the chuck so I don't understand how the insert edge could cut differently part way through unless it was a onetime occurrence that started just having the edge go bad.
None the less, I flipped the insert to a new corner and consistency improved! However I am not getting as smooth as a finish as I was at least on the one end of the piece. I suspect that is because the old edge was rubbing more than cutting??? Even under magnification the old insert edge looked almost perfectly fine, I could tell it was used but that's about all.

 

[DPittman]

Inspect the edge of your insert. Around mid point on your piece is a mark, and then the chatter got worse.

Interesting. I seemed to get this chatter repeatedly near the chuck so I don't understand how the insert edge could cut differently part way through unless it was a onetime occurrence that started just after having the edge go bad.
None the less, I flipped the insert to a new corner and consistency improved! However I am not getting as smooth as a finish as I was at least on the one end of the piece. I suspect that is because the old edge was rubbing more than cutting??? Even under magnification the old insert edge looked almost perfectly fine, I could tell it was used but that's about all. View attachment 30251

Your problem may be self induced.

Since one end is on a center and the other is not you may have a bit of bend moment at the chuck end, ideally you should run between centers with a dog.

If thats not possible, loosen the chuck a little and retighten lightly, again a just a touch of pressure on the center.

Oh also very interesting and could very easily be the cause! I did have the work piece twist out of the chuck earlier when I was "testing" to see how deep of a cut I could make, and stupidily I was not using the tailstock at that moment.

 

[Tom Kitta]

I would eliminate all other possible causes before blaming the bearings. I would certainly run between centers with known steel & known insert.

I would also repeat the test with new insert / type & different stock.

A bad bearing would get hot at higher speeds / would make noise. Also with an indicator it would show runout. This is as far as my know how is. I only dealt with this problem once in my life.

 

[DPittman]

I agree with @thestelster.

Also, your chips are those nasty tight long curlies. Those are notorious for getting caught under the tool and wreaking havoc! Check the data on your insert regarding speed, DOC, and Feed Rate for better chip breaking performance.

I can't yet recognize inserts by material. Check to make sure it is compatable with the material you are cutting.

If all else fails, try HSS......!

I'm not suspicious of your bearings just yet.

I've been switching between turning tools and some of the worst long curries were likely form hss in my diamond tool holder which has no chip breaker.

 

[Susquatch]

I've been switching between turning tools and some of the worst long curries were likely form hss in my diamond tool holder which has no chip breaker.

Yes, I have the same experience. But for some reason (likely the sharpness of hss), I can have long curlies with hss and never have this same problem that I have with carbide. But if I make the carbide chip breaker do it's job and make small chips the problem goes away there too.

 

[DPittman]

I would eliminate all other possible causes before blaming the bearings. I would certainly run between centers with known steel & known insert.

I would also repeat the test with new insert / type & different stock.

A bad bearing would get hot at higher speeds / would make noise. Also with an indicator it would show runout. This is as far as my know how is. I only dealt with this problem once in my life.

Yes I put on a dial test indicator on the work and with quite heavy pressure on the chuck I could only get .02mm of play. I checked if I could snug the bearings up any and felt that any tighter would be detrimental. I don't think my bearings are the problem. I didn't think they would be bad but I thought they could have been a bit loose.

 

[PeterT]

All it takes is a tiny amount of insert fragmentation resulting in poor finish. But I would have expected consistent rough surface down the entire length, not just local proximity to the chuck. Now maybe edge started out OK on the RHS, started to fail somewhere in the middle, so then crappy to the chuck. Now if you began a new pass & crappy the whole way that would make sense? Especially if swapping the insert edge fixed it. Is that the order?

Usually when you have a repeat finish problem in the same local area its things like power feed drive assembly (junk in the power feed bar or screw, slightly misaligned bar or bent that is staring to choke up on the worm drive etc.) If you can manually displace the carriage along by hand with good finish, but a patch of bad finish under power feed, then something in the power feed assembly could be contributing. Less likely but also a possibility is surface condition of the bed rails in that area. But it would have to be a healthy dent or embedded chip or maybe gap insert related?

 

[140mower]

Have a look at the photo and hopefully you can see the chatter marks increase as I get towards the headstock. I have the other end supported by a small live center in the tailstock. My first suspicion is loose spindle bearings but last I had checked there was no obvious sign of that. I will check again after this job but thought the picture might be helpful to others whatever the problem may be.
Any suggestions or tips are always welcome.

Edit I forgot to mention the turning g was done under power carriage feed so travel speed (and depth) was consistent.
View attachment 30250

I had the same issue the other day..... In my case, yes it's the bearings, I had really no time to dig into it at the time and will dig on a little more when I get home again. To get through, I reduced the depth of cut and it mostly went away. Enough to get what needed done, done. In my case its a split bronze bearing and it looks like someone added a shim. That is where I am going to start with mine....

 

[thestelster]

What is the material you are turning? What depth of cut and feed?

 

[Proxule]

Apron / saddle keepers should be set to anout .001 clearance.
Tighten gibs.
Adjust tailstock center

Etc etc.

Although setting a DTI on you spindle nose and pushing or pulling on your spindle or gently tapping with a dead blow will inform you.... save spindle adjustments to the end.

My 10x22 had the same issues and manifestation..... was spindle bearings.

Gluck

 

[DPittman]

Apron / saddle keepers should be set to anout .001 clearance.
Tighten gibs.
Adjust tailstock center

Etc etc.

Although setting a DTI on you spindle nose and pushing or pulling on your spindle od gently tapping with a dead blow will inform you.... save spindle adjustments to the end.

My 10x22 had the same issues and manifestation..... was spindle bearings.

Gluck

I'm sort of leaning back to maybe bad bearing again. They seem to be running warmer than I think they should be, and used to maybe.
Did you do any upgrade of bearings when you replaced yours?

 

[DPittman]

What is the material you are turning? What depth of cut and feed?

Mystery metal. When I was getting the smooth finish to start with then when it got worse towards the chuck I was using .020"-.030 DOC and carriage travel approx .002"/rpm and I believe I was using about 900rpm

 

[thestelster]

Mystery metal. When I was getting the smooth finish to start with then when it got worse towards the chuck I was using .020"-.030 DOC and carriage travel approx .002"/rpm and I believe I was using about 900rpm

0.020" - 0.030" is fine. Try increasing your feed to .003-.004"/rev. and see what happens.

 

[DPittman]

0.020" - 0.030" is fine. Try increasing your feed to .003-.004"/rev. and see what happens.

I'm going to have to try experimenting on new material (probably will be mystery metal of some kind also) as that particular piece I was turning is finished. What is really baffling me is how it changed surface finish close to headstock.