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PM 935 TS Spindle Run-out

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ddickey

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#1
Wasn't really planning on doing this but I got bored trying to figure out my vfd so threw a DTI on inside spindle taper. .0005" TIR.
Next I put a precision ground rod 1/2" and got .00075" TIR. Made a mark of the high spot and then dropped the table 3.5".
The high spot moved .001". I was getting .002" high of zero and .001 low of zero so .003" TIR at 3.5".
Oh, and after dropping the table I raised it just a little to take the backlash or whatever it is out.
I'd like to know if anyone did some tests on theirs and how it turned out.
 

wrmiller

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#2
I measured the inside of the spindle, on the taper and it barely registered. I stopped there because anything else is more indicative of the accuracy of tooling/tool holders and mine are not Hardinge quality, so it is what it is.

I guess I'm more of a end result kind of guy and so far I've been very pleased with my 935 TS. It's way more accurate than I am.

I hope you have as much fun with yours. :)
 

ddickey

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#3
Outside of my taper was .001"
Although that really means nothing.
 
Last edited:

pacifica

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#4
Wasn't really planning on doing this but I got bored trying to figure out my vfd so threw a DTI on inside spindle taper. .0005" TIR.
Next I put a precision ground rod 1/2" and got .00075" TIR. Made a mark of the high spot and then dropped the table 3.5".
The high spot moved .001". I was getting .002" high of zero and .001 low of zero so .003" TIR at 3.5".
Oh, and after dropping the table I raised it just a little to take the backlash or whatever it is out.
I'd like to know if anyone did some tests on theirs and how it turned out.
Seems high.
 

ddickey

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#5
That is very rare for these. I've talked to Matt. My precision ground bar can not be used however. Matt pointed out the tolerance is .002"/ft.
I suspect it's worse than that.
 

wrmiller

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#6
The only surface that matters is the taper that the collet registers on, or so I thought. And you used a collet to hold the ground rod? What's the tir on the collet?

I'm not a machinist, so I'm trying to figure out what exactly you're measuring here? Thanks.
 

ddickey

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#7
The only surface that matters is the taper that the collet registers on, or so I thought. And you used a collet to hold the ground rod? What's the tir on the collet?

I'm not a machinist, so I'm trying to figure out what exactly you're measuring here? Thanks.
That's correct, the inside is the only thing that matters. .0005" max run out for the collet.
 

mksj

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#8
The accuracy of R8 and 5C collets can often can be problematic, their TIR can be several fold worse then the spindle and you can also see significant axial run out as you you go further away from the collet. I use a Haimer edge/center finder which has a repeat accuracy of 0.0004", when I tried to set the tip alignment, I quickly found that the collet TIR was much worse and so had issues of not being able to set the tip alignment. I ended up having to use an ER32 collet system that I could verify that the TIR was ~0.0001" for a precision pin. I also found that my 0.0005" indicator just didn't have the sensitivity/accuracy to align the probe tip, I use a Compac 0.0001" test indicator and was able to get the Haimer to repeat per spec. The Haimer has a 12mm shaft, so initially was using a Shar's 12mm R8 collet, but the TIR was ~0.0006", so pretty bad. I replaced it with a Royal R8 collet which was vastly better. As other mentioned, a direct reading of the spindle collet mating surface it what counts, then getting a decent set of collets/chucks. I would expect spindle run out on higher end machines to be in the 0.0001-2" range.
 

Bob Korves

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#9
To test a spindle, test the spindle, not the collet or other intermediate tooling, which only confuse the issue.
 
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