PM835S spindle run-out

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Batmanacw

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My PM 835S spindle has always be crazy accurate. Run out less than 0.0001". Endmills in r8 collets run out 0.0002" or so.

I had been playing around with er collet chucks and trying to get top quality tooling for the best accuracy.

Turns out I took too heavy a cut last week and it appears I bent my spindle a bit. Now I have a solid 0.0002" tir at the spindle nose and every collet and collet chuck runs out 0.0005". Up to 0.002" at 4xD.

I'm pretty sick about it. Half a thou is still plenty useable. I'm just not happy I damaged the spindle. I'm going to look into a new spindle just because.

It's not contamination in the spindle or a loose spindle nose. I checked several spots on the taper. It's definitely honest run out.
 
That sux. Just doing a heavy cut did that? There must be more to the story.
 
The only other thing that might have contributed is that I started using a torque wrench to tighten my drawbar to 25 ft lbs. It made the tools pretty snug with the drawbar being lubricated. I wonder if the spindle is bell mouthed instead of straight up bent?

When I looked for a maximum torque value for the drawbar I found 40 ft lbs as the max. I never imagined 25 ft lbs would hurt anything.
 
  • High Precision Spindle with +/- .0002” or less runout for greater tool life and accuracy
Quoted from the PM website .
 
mmcmdl said:
  • High Precision Spindle with +/- .0002” or less runout for greater tool life and accuracy
Quoted from the PM website .
Click to expand...
All my tools are running out 0.0005" at the nose and 0.002" an inch out. It was much better before. The bore isn't in line with the taper anymore. Used to be 0.0005" at 4xD.
 
I've requested a quote on a new spindle just to see how bad it would hurt to get it back to dead nuts.
 
When I was trying to check out the run out issues with my collet chucks I noticed a few times the taper didn't lock in the spindle. I decided to check the taper with sharpie on a Lyndex-Nikken Japanese made collet chuck and some sharpie.

This is what I found.

 
PM is getting me a price on a new spindle. I'm going to talk to a local company about lightly dusting the old spindle to get rid of the bulge.
 
A couple of suggestions.Try cleaning the spindle taper with a very fine scotch brite pad. Then measure run out directly on the spindle taper at multiple locations. If you see excessive run out note if it is happening in a narrow strip or in a more generalize manner. Mark the high spot with a sharpie then run the machine for a minute and repeat the measurements. Did the high spot move or remain in the same place?

If it moved then you may have a bad bearing.
 
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