# R8 Round Collets



## EmilioG (Dec 10, 2016)

I recently purchased a few Hardinge R8 collets so I could have at least a few accurate collets in my collection, and I noticed that the Hardinge 3/4" R8 collets have a looser initial grip than cheap import collets.
They go in the spindle and tighten up really well, but I have to hold the tool or arbor when putting it in the spindle or the tool will fall out.  Is this normal? I haven't checked run out yet.  Are there any good USA made
collets that aren't $42 each?


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## RJSakowski (Dec 10, 2016)

I bought a 3/4" R8 collet made by Crawford in the UK from Wholesale Tool because it had the best quoted runout spec at the time.  The current price is $18 each.
http://www.wttool.com/index/page/ca...&results_per_page=20&order_by=&search_params=


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## EmilioG (Dec 10, 2016)

Did you check run out on the Crawford collet?  I maybe a couple.  I have two imports and the rest are Hardinge, Bridgeport, News Japan, &  Lyndex .
Is the Crawford 3/4" collet "loose" or tight grip?  I theorized that the size of the slits on such a large opening on an R8 round collet will give it more "spring", thus creating the "loose" initial grip before it's put into a spindle.  Not sure.


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## Tony Wells (Dec 10, 2016)

If that's a used collet, someone probably has sprung it open a little. Not much you can do about that. Just watch your fingers when putting in a new end mill. The edges can slice you open if it tries to drop and you grab it wrong.


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## RJSakowski (Dec 10, 2016)

EmilioG said:


> Did you check run out on the Crawford collet?  I maybe a couple.  I have two imports and the rest are Hardinge, Bridgeport, News Japan, &  Lyndex .
> Is the Crawford 3/4" collet "loose" or tight grip?  I theorized that the size of the slits on such a large opening on an R8 round collet will give it more "spring", thus creating the "loose" initial grip before it's put into a spindle.  Not sure.


It will grip a Tormach TTS ER20 collet chuck which weighs in at a little under 1 lb.  As far a runout goes, I did check it but I don't remember what I got.  At the time I was concerned with the runout with  the Tormach 3/4" R8 collet used in their TTS system.  The measured runout was in the machine using a 3/4" wrist pin so runout was a combined runout for spindle, collet, and pin.  From recollection, I got better runout on my old mill/drill.

I just did a quick check on the mill/drill and TIR with the 3/4" pin was less than .0002" at 10mm from the collet face and at 25mm from the collet face.


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## EmilioG (Dec 10, 2016)

RJ, that is pretty good, .0002".  AFA that used 3/4" r8, I'm only using it for 3/4" arbors.  I'm going to buy a new Crawford
to check those out.  Thanks all.


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## Bob Korves (Dec 11, 2016)

If you put index marks on the collets (and other tooling) and the spindle showing the high or low spots, you can quickly index them during installation to help cancel out any runout rather than becoming randomly additive or subtractive.


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## EmilioG (Dec 11, 2016)

Bob Korves said:


> If you put index marks on the collets (and other tooling) and the spindle showing the high or low spots, you can quickly index them during installation to help cancel out any runout rather than becoming randomly additive or subtractive.



Thank you.  Does this indexing apply to all collets or just the imports?   I watched a video once where the machinist put his mill taper spindle on a lathe to true up
any run out in the taper itself.  The collet will go in a bit deeper but doesn't affect function.


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## Bob Korves (Dec 11, 2016)

With any tooling you can cancel runout if you index the high of one portion with the low of another portion.

Here is a demonstration of repairing a mill spindle in a home shop:




Note, however, that if you have a spindle .0005" out and a collet .0005" out, you can cancel the runout by proper indexing.  If your spindle is true and the collet is out .0005", then you cannot further reduce the combination.  This is of course for fussy work, not everyday milling.


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## EmilioG (Dec 11, 2016)

That's it. The video I referenced.  You can have this work done by Pro's, not sure on cost.  
I would also make sure the die grinder was running
fairly true.  Dotco die grinders with Dotco collets.  I think it's worth the time and effort.  That's just me.  Thanks


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