Er 32 collet issue

[stirboy01]

bought an inexpensive collet set which came with runout issues.. it is a mt3 spindle insert into the head stock and has no runout measured right by the headstock spindle.. the taper in the collet holder is basically dead on measured at several depths ( which is great ) .. problem being the od of the holder body and threads for the lock nut (bearing type) are out about 0.004 which throws the od of locknut out 0.004 when installed.. im sure this imparts issues on the inner workings of the collet nut when trying to tighten collet into holder.. im thinking about taking a couple thou off the threaded portion of the holder od to help align nut to holder body .. any thoughts b4 i whittle it down ? thanks stirboy

 

[WobblyHand]

Have you tried putting in a ground rod, or some other known good rod in a collet and measured the TIR? Have you tightened down the collet nut tightly? These collets require you tighten them pretty snug. Some folks here advised the required torque was near 100 ft-lbs. I don't do mine that tight, but I torque them a lot closer to 100 than to 10. This should help snug the collet to the taper which you have measured to be true.

Speaking of which, how did you measure the runout? A picture is worth a 1000 words.

 

[Logan Novice]

The exterior surface runout can be dead on but, if the center is not running true, that won't matter much. I'd suggest you clean all mating surfaces, load a known dead nuts accurate gauge material (drill rod comes to mind) into the collet, tighten that down REEEEEL tight, and see how that runs.

 

[markba633csi]

I think the outside dimensions are not guaranteed to be as close as the inner taper and shank portions
It may or may not be a real problem- check with a known good piece of rod like Logan suggested
-Mark

 

[brino]

Did you install the collet into the nut _before_ putting it into the MT-3 to ER-32 adaptor?

The ER-32 nuts have a small off-centre lip that needs to engage in the collet groove.
It is used to extract the collet from the taper and let go of the part.

If you don't do it in this order then that off-centre lip tries to push the collet off centre as you tighten the nut.

-brino

 

[markba633csi]

I think all the ER series are the same; the collet goes into the nut first
-M

 

[T Bredehoft]

Just a suggestion, use a dowel pin, not a piece of O1 drill rod. The O1 is ground in a centerless grinder, may have as much as .0003 or .0004 3-lobe effect.

 

[Logan Novice]

Just a suggestion, use a dowel pin, not a piece of O1 drill rod. The O1 is ground in a centerless grinder, may have as much as .0003 or .0004 3-lobe effect.

Here's a little help for that good idea: https://www.mcmaster.com/dowel-pins/diameter~5-16/oversized-dowel-pins/

 

[stirboy01]

thanks for the reply's !! after some more thought into the issue i think i need to rethread the od of the chuck rather than just taking a couple thou off the od.. the root of the thread will still be the same amount off in relation to the 8 degree taper of the chuck and will not let the nut center up with the internal taper for the collet .. problem is i dont have metric gears to run the 1.5 metric pitch on the od of the holder.. thanks stirboy

 

[T Bredehoft]

I thought maybe an Imperial thread would be close, but.....1.5 mm equal about .0059 thousands lead, or 16.993 (17) imperial pitch. Memory tells me there ain't no such animal. Sorry had to share my disappointment.

I had to check, too. Machinery's Handbook ignores the number 17 in it's chapter on threads. Not even a fatherless (bastard) pipe thread.

Edit: correct typo.