thank you all for the info. As grifter pointed out I was measuring the inside taper of the collet chuck itself, not a pin in a collet. I was concerned that there was something going on deeper inside the spindle R8 taper but i think I effectively ruled that out because my R8 collets have .0001 to .0002 runout. I would think that would rule out a draw bar issue as well but not sure. Its a PM 935 mill.
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ER 40 Collet Chuck Runout
- Thread starter weejax
- Start date
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- Jun 12, 2014
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- 5,053
It still should be in the ballpark, Glacern are usually quite good so sounds like a bad run. PM-935 are well made, be very surprised if the spindle was off, but I would sweep the inside to see what the TIR is with no collet, also try to feel if there are any burrs or contamination in the spindle. The R8 arbor fitment if off I would expect to see similar deviations with other R8 collets/arbors. Only other thing that could cause a problem if the your are using the R8 alignment pin and it is too deep and pushing the arbor slightly to one side. Previous post on the subject.
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R8 ER32 Chuck?
I bought a cheap China R8 ER32 chuck (I know) anyhow the runout is about .o12 on a short piece of o2 drill rod. The taper in the ER32 has .006-.007 runout. My question is does anyone have a suggestion where to buy another one that is better quality.
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Spindle runout is < .0001 on PM 935. I checked a 1/2 R8 collet indicating on an endmill and got .0001 TIR. On 3/8 collet/endmill i got .0002-3. I even tried my R8 drill chuck indicating on the 1/2 end mill and got .0004 TIR. So I dont think its the spindle. I thought about the alignment pin--all the collets go in smooth and have slight play when the pin is in the key way but not tightened down. I did the same thing in my smaller mill and got similar results--standard R8 collet with about .0001 TIR, but the ER 40 had around .0015 TIR this time (it was reading around .0008 on the PM 935). At this point I guess im going with the ER40 collet being bad. But still second guessing if im missing something. I guess i can try taking the alignment pin out or moving it in and see if it makes a difference. but i need to get a tool. thanks for all the help.
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- Jun 12, 2014
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Skip pulling the alignment pin, if you get that degree in two separate machines it is clearly the arbor. I am really disappointment at what is available these days, at the price of the Glacern, you might check out the TMX/Bison R8 ER32 arbor, I do not know if it comes with a nut wrench. Seems like very few options. I have a few of the Shar's arbors, and those made in Taiwan (their upscale brand) have been quite good. Replace the nut with a better quality one from Techniks or Regi-Fix. Bearing nuts help reduce the force needed to tighten the collet, recommended. I use the Shar's and ETM, both have been fine.
www.shars.com
www.shars.com
R8 ER32 ER Collet Chuck Tool Holder
ER 32 Ball Bearing Collet Nut
I went ahead and ordered an accusize from amazon. I was excited when i got .0002 on the OD. But the ID had 1.5 thou. Decided to see what happened when I took alignment pin out. Nothing changed (except now my spindle return spring doesnt seem to work as well). Sent back both glacerns and the accusize. I guess I will try shars.
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- Dec 18, 2019
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- 7,295
I've been very pleased with the Shars set tru ER40 chuck. I made a back plate for it, because at the time, they were out of stock. You can dial in any minor offsets to have it run with 0.0001" TIR or under. https://www.shars.com/5-er40-zero-set-fine-adjustment-collet-chuck
Edit: Here's the back plate being turned. It was a little messy! Learned a lot doing it.
Edit: Here's the back plate being turned. It was a little messy! Learned a lot doing it.
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I'm getting a 1340gt soon. I ordered the er40 lathe chuck from PM. Hope it is as good as the Shars. The chuck I was referring to above us for a mill.
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- Dec 18, 2019
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Sometimes you get a bum part. You could try again with them. Or start the search again.
I've had quite a few off spec parts come my way. All you can do is to keep on trying. Or you can make some of your own tooling. Have to say, it seems to come with the territory.
As for being in spec, what counts is the installed performance - as used. Of course that implies your equipment is in spec too. Sometimes it isn't. Check it , as it's more difficult to get low TIR if your spindle or equipment is an error contributor.