Sudden Onset Chatter Issues - riding the struggle bus and need some HELP, please.

We are hearing you, it’s just a very hard problem to diagnose from a distance. We can only offer anecdotes based on our own experience.

For example, the front bearing on my heavy nine was a little loose as were the headstock bolts. There was no chatter but I was chasing down deflection issues (parting mostly). Now I have seen exactly that same issue, just yesterday in fact, with a couple of cutting tools that either had insufficient clearance or a small chip at the tip. Awful cyclic chatter marks just like that. Changed to a sharp hss tool and the problem went away. Certainly doesn’t mean doing the same would solve your issue, just saying that it solved mine
 
I do really appreciate all the suggestions and that this would not be an easy thing to diagnose. I wasn't so much looking for that (although it would have been great!) but I'm more looking for suggestions on anything else I haven't looked at. Which is why I tried to list all of the things I have been trying to rule out over the last week. When I get the same result with a half dozen different tools, I'm pretty sure that reduces the likelihood that it's the tool pretty significantly. :)

I've cleaned everything I can think of - spindle threads, chucks, chuck jaws. I pulled the QCTP and cleaned the compound, cleaned the nut for the QCTP before putting it back on. Cleaned the tool holders. Made sure there were no chips under the inserts. Torqued the insert screw. I even went so far as to swap out the tool post for the lantern tool holder and tried that one. No joy.

I'm going to try some experiments this evening, changing feeds and speeds. But the problem I am having is this is the same setting I use for 99% of the turning I do on this lathe. I change this gear only when I am threading. I even tried hand feeding and got the same results, so I don't see it being the feed speed, but it's not like I can move the carriage wheel at a consistent rate.

If it's the motor, I don't even know how I can diagnose that. That should prove challenging to say the least.

So frustrating. Something is wrong and all of the obvious things seem to check out OK.
 
I have a 14.5” south bend. I had the exact issue and checked everything. The thrust bearing needs more pressure. Remove the gear cover. Loosen the screw on the lock collar and use a strap wrench on it until it is tight. About the same torque you would use for the tailstock nut for a center drill. Even if it is a bit tight it is not enough. Let it chatter long enough and that collar only gets looser to where you can see the work move in and out.
 
Curious to see what it turns out to be- can't visualize what would suddenly break and cause it that you wouldn't readily notice
 
2 suggestions.

For thrust check, place dial indicator in tool post measuring end of work.

Tap towards headstock then opposite to see movement.

If you make adjustment, measure the marks in work before and after.

To test motor, switch to different speed, if marks stay same space then it is not motor.

But consider the drive "system", change to back gear as well.

If this is power feed, try by hand, a loose interface in the drive can cause inconsistent feed rate that you may not see.

Change only the sliding gear on the left side and test, if no change, put back and try different feed rates.

If single lever try all 3 positions, if 2 lever, try each.

A worn gear or bushing could cause this.

We have seen similar with some materials, increasing the radius on your tool, or using a corner shaped instead or pointy one may help.

End play in the acme screw allows the carriage to shift depending on the force needed to cut, softer spots is slides along, harder spots it may not move as fast until end play taken up.

Place dial indicator at tail stock end of drive and see if it has end play, easy to adjust.

With lathe off, 1/2 nuts on, carriage close to head stock, use 2x4 to push away, use webs in bed to push back.

Move dial indicator to measure carriage movement reference to bed and repeat, this is both drive end play and 1/2 nut side play in carriage.



Sent from my SM-G781V using Tapatalk
 
This probably won't apply, but might give you some ideas; but, you may want to check this thread regarding the chatter on my SB 9 Junior lathe.
www.hobby-machinist.com

Lateral Spindle play causing Chatter SB9 Junior?

When turning with my SB9 Junior, I get some chatter and rough with what appears to be an oscillating vibration on the lathe. Thought it was the way the self contained motor unit is mounted; but that has been redone and is not the issue. For more info on this lathe, see this thread...
www.hobby-machinist.com www.hobby-machinist.com
I hope you find the issue.
 
I am still trying to chase this down. While I had the spindle out, I checked everything as best I could. The front bearing surface has some galling on it, but no more than what was there when I had it all apart 3 years ago. As best as I can measure it, the spindle is straight. When I had it apart the first time, I replaced the thrust bearing and also replaced the rear felt washer with a thrust needle bearing. I replaced them again today.

I ended up replacing the front bearing cap shims with a set from eBay. Installed, the front bearing was within the .0007 to .0010 spec without removing any layers. The rear ones were too thin. Slightly snugging the rear bearing cap screws and the spindle binds up. So I put the original ones back in. I did end up removing one layer off of one shim to get it within spec. Both the front are rear bearing clearances are within spec. I ran the lathe for a while tonight, but I will check them again over the weekend.

I also tightened the V belts between the motor and the countershaft. They were a little bit loose. Not overly loose, but likely stretched a bit.

I did some test cuts. It's better. Not as good as it was, but it is better. Depending on material, that is. 12L14 machines pretty much perfect. Where the 1045 that I had no issues with a couple of months ago is now giving me fits. I machined a new splined shaft from a stick of 1045 and didn't have any of these issues.

I didn't notice any rocking in the saddle, but I am going to recheck it this weekend. I'll also recheck the stuff that tq60 mentioned. I need to document all of the steps and results or I'll lose track of what I did. :)

So my next this to try is to drop the motor and check/replace the bearings. I don't want to drop the countershaft unless I have to. That would likely be the last resort in trying to chase this down.

It could have been a combination of a bunch of things all coming to a head and correcting some of the little things is giving me some improvement? We shall see.
 
I couldn't see from the videos and this is just a really left field idea that maybe, is probably, bollocks :oops: but since you've been pretty rigorous in controlling the variables in your investigation and so far, discounted the obvious suspects...

Given chatter can be the result of some kind of harmonic amplification of a standing wave of vibration, could your problem be caused by something physically connected to the system (i.e. the lathe) but not part of it?

I'm thinking of your lathe mounting setup; bench, stand, raiser blocks, etc.

Is it possible, something in that 'chain' has shifted or loosened up, and where before the mounting setup would have had no effect (or even acted as a sink or to damp vibration), it's now acting as amplification of vibration at certain frequencies?

Just an idea for consideration (and dismissal as daft if you like; I won't take offence :)).
 
This is the material. I made a shaft from 1045 about 6 months ago and the Finish came out as in your pictures.
I was using a customer's machine , a 4 year old lathe.
Some of the other structural steels quality has fallen as well.
They will work as the specifications fall within tolerance for the material but your not getting any extra quality.
Bet you try a good quality steel you will find you and the machine aren't at fault.
 
sdelivery said:
This is the material. I made a shaft from 1045 about 6 months ago and the Finish came out as in your pictures.
I was using a customer's machine , a 4 year old lathe.
Some of the other structural steels quality has fallen as well.
They will work as the specifications fall within tolerance for the material but your not getting any extra quality.
Bet you try a good quality steel you will find you and the machine aren't at fault.
Click to expand...
Oh, well, that's an interesting proposition.:)

It's easy to assume that materials of a given spec remain as machinable as they've been befor (I mean, that doesn't seem an unreasonable expectation) but external factors (and with the recent and current volatility in pretty much everything in the world, that's a lot of external factors!) could definitely have an impact on the quality of materials.

Whether that's the cause of the OP's problems remains to be seen, but on my behalf, thank you for making me think about this. :) :encourage:
 
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