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

[Janderso]

Maybe I missed it but have you made sure your gibs are snug?

 

[MyLilMule]

Well, I can't say for sure if it was ONE thing, but I have my suspicions on what it was.

What did I do:

• One of the rear leveling feet had come partially off the rubber pad, so I fixed that. I doubt that was it.
• I adjusted the V belts on the motor a little tighter. Specification says I should be able to press them together about 1".
• I did check the bed for twist and didn't find that there was much twist at all. One end was maybe out of "level" by .0008" over 10" - as precise as my cheap chinesium level can measure - .0002" over 10". The bubble was off by 4 tick marks. On a 5 foot bed, trying to get that out of it using leveling feet is a fool's errand. I tried, but made 0 progress.
• I pulled the spindle and inspected everything. I set the spindle in the head stock bearing caps, put in indicator on it in multiple places, and saw no evidence of it not being straight.
• I cleaned and stoned the front spindle bearing surfaces, on the spindle itself and inside the bearing caps. There is galling on it, but it's been there since before I've owned it, and it was never an issue before. Stoning it probably didn't do much at all. But if there were any burs, they are gone now.
• The rear spindle bearing surfaces were perfect.
• I stoned the mating surfaces of the bearing caps.
• I flushed the front bearing oil sump and replaced it was new spindle oil. It was dirty - not surprising since it's the business end. The rear was perfect.
• I bought a new set of layered bearing shims from a seller eBay.
  • The rear shims were too thin out of the box so they were useless. I ended up using the originals, but I did remove one layer off one shim to get the spindle play within spec. (.0007" to .0015")
  • The front shims were also too thin, but I was able to use them by adding a .0015" shim to one side of the bearing cap. That put the spindle play within spec.
• I replaced the thrust bearing that's between the cone pulley and the rear spindle bearing.
• I replaced the rear needle thrust bearing that is between the rear bearing cap and the take up nut. From the factory, this is a felt washer, but I think the needle thrust bearing is a better replacement.
• I adjusted the take up nut so there is .001" fore and aft play in the spindle.
• Along with the menagerie of other things I already checked and mentioned before.

The verdict:

This is some DC 53. If it was going to chatter, it would have. My lathe doesn't like this stuff much. I also tried a piece of the same stuff I used in previous posts. It's back to normal. Yay!

What do I think it was? I think it was the take up nut (mostly) and the front bearing clearances combined. When I removed the spindle, I felt like I remember the take up nut being a little loose. Not like flopping around loose, but just didn't seem like it was tight. Although I could be misremembering or merely hoping I have something at which to point. One of the tests I did was to tighten the take up nut, not knowing at the time that it needs to have some play, and that probably made it worse. I think it backed off a little as some point. And I think that plus there being TOO much play in the front spindle bearing cap, was what it was.

Lessoned learned: Do at least a yearly checkup on all bearing clearances, belt tension, etc.

Thank you again to all who offered suggestions. I read them all, even though I did not reply to all of them. You gave me hope!

That's fixed! On to the next job!

 

[mattthemuppet2]

fantastic and great to hear what you did to get there. As I was reading your trials and tribulations, I figured that at the very worst after all you've done you would have given your lathe a very thorough service