On Tuesday 12 April 2016 11:33:16 Todd Zuercher wrote:

> Techniks sells nuts that they claim are better than ball bearing nuts,
> because of their "Powercoat".
> http://www.techniksusa.com/metal/pwrctnt.htm
> And they do tighten down very nicely, at least when new.  After
> they've been used for a few years I'm a bit skeptical.  I've found the
> finish does wear off of the collet contacting surface fairly quickly, 
> I think the tightening advantage comes more from the coating on the
> threads, that seems to last longer than the part against the collet
> nose.  Still it does wear off eventually.
>
> How often should these things be replaced?  We have some that have
> been in service for 10+ years of multiple daily tool replacement. (and
> it shows.)
>
> Worst tool holder/nut combo I've used were some HSK63F ER40 tool
> holders from T-ToolUSA.  We've had a lot of trouble with the threads
> on these nuts and tool holders galling.  One hung up so bad I almost
> couldn't get it off, tearing out large chunks of thread in the
> process.  And these were only torqued to 90ft/lbs (using a proper
> torque wrench).

I haven't yet experienced any of that, but ER-40's are way above my pay 
grade as the biggest spindle I have is a 1 horse, spinning an R8 socket.  
I do use a 10" crescent to pull these up once the spindle is pinned but 
doubt if I've ever exceeded 50 lb/ft even when trying to keep a tap from 
slipping. My spindle pinner is home-made, and any more torque than that 
may shear the mounting bolts holding the block carrying the pin to the 
clamp collar on the spindle housing.  TBT, I didn't use a big enough 
pair of bolts. 4mm's IIRC.

I did get a full set of 1-13mm ER20 metric collets just now too, so I 
should be able to get a decent grip on the shank of most any tap my 
spindle can turn. 3/8-18 and 10mm need lots of fractional turn pecking 
so I'd best not try anything any bigger anyway.  ER20 collets with 
square rear sockets can be had, at seriously ohmygawd prices though.

Thanks Todd.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>

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