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

MyLilMule

MyLilMule

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Cross posted to PM.

About a week or so ago, my 13" South Bend started chattering like crazy. It's REALLY bad. And I am at a loss as to why. I've owned this lathe for 3 years and never had any serious issues with it.

I attached a video of the bearing clearance checks as well as some video of cutting a piece of mild steel - a piece I have machined on in the past with no issues. I've tried several pieces of stock and can't seem to figure this out.

What I have checked:
  • Spindle bearing clearances. Within tolerance (.0007" to .0010"). If any more shim is removed, the spindle binds up.
  • No detectable fore and aft spindle play.
  • The spindle is being lubricated. The reservoirs are full.
  • Swapped the 3-jaw for a 4-jaw with the same issues (No spindle collet setup for this lathe)
  • Checked the headstock bolts and they are tight
  • Screws attaching the saddle to the apron are tight.
  • Checked the cross slide gib. It was tight. It has some wear so a shim was added just in case.
  • Compound gib is fine. Tightened it to the point it's difficult to move. Problem persists.
  • There's backlash in the cross slide and compound lead screws, but not that much that it's concerning. No change since it's been in this shop.
  • Swapped QCTP's with my other lathe.
  • Swapped compounds with the other lathe. No luck.
  • Checked the saddle gib and it's tight as it can be.
  • Tried varying spindle speeds and turning speeds with no significant change in surface finish.
  • Tried three different insert geometries that have been perfect for me in the past.
What am I missing? What is left to check?

Help me Obi-wan Kenobi, you're my only hope! ;)

 
Last edited:
I didn't watch the video, but I'll throw these out there.
I had a problem and it turned out to be that my apron to carriage connection.. the screws loosened up and it was not a place I was checking.
Went to tear things apart and found that, stopped tearing it down and just tightened and the problem was solved.
 
Not familiar with the south bend, but does the tail of the spindle run on a set of bearings?

On my Logan, one of the bearing cages broke on the tail bearing and it broke in several spots. Had awful chatter.
 
woodchucker said:
I didn't watch the video, but I'll throw these out there.
I had a problem and it turned out to be that my apron to carriage connection.. the screws loosened up and it was not a place I was checking.
Went to tear things apart and found that, stopped tearing it down and just tightened and the problem was solved.
Click to expand...
Inadvertently left that off my list. Those were checked and are tight.
 
Dyspnea said:
Not familiar with the south bend, but does the tail of the spindle run on a set of bearings?

On my Logan, one of the bearing cages broke on the tail bearing and it broke in several spots. Had awful chatter.
Click to expand...
The bearings are cast in the headstock on this model. There are no separate bearings. There are thrust bearings on the spindle, but those all looked OK when I checked them.
 
Another source that I'd consider, although not likely, is something in the motor, electrical power, VFD if present, or drive belt and pulleys.
 
ok, just watched it.
at first I thought it wasn't chatter but a too sharp a radius on the tool.
But later in the video it is clear it's chatter.

Still, have you tried a tool with a much more rounded nose?
Have you tried oil?
Have you tried a slower speed?
Have you tried a much faster speed with a slower feed? again with a faster feed?

Do you feel anything if you put your finger on the holder while it's cutting?
I don't hear the typical chatter sound.

one more thing. I have a SB although a 9 with cast iron bearings. Is you spindle well lubricated? are the felts clean or very old?
if it's not getting lubrication, it could be a spindle issue? Is the headstock getting hot, or the spindle.
 
I think you should try another material
 
Have you tried a different tool bit? It does look like something is loose though.
 
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