6mm shanks and 1/4" collets

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Forum topic by henigail posted 05-28-2013 07:32 AM 11009 views 0 times favorited 9 replies Add to Favorites Watch
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12 posts in 1835 days

05-28-2013 07:32 AM

Hey guys, does anyone know if a 6mm shank can be used in a 1/4” collet? I recently bought an Auriou rasp, and I like it so much I decided I’d also like to have a powered version, so I wanna get one of their rotary rasps to use in my die grinder.

Problem is they seem to only come with 6mm shanks and my grinder (obviously) has a 1/4” collet. The difference is only .01378, but I guess this might be significant enough to pose a problem…definitely don’t want this thing flying out of the grinder while spinning.

If the answer to that question is “probably not,” does anyone know where I can find a 6mm collet that will fit my die grinder? I’ve looked but couldn’t find.


Does anyone have recommendations for another brand of HIGH quality carving burrs/rotary rasps (with 1/4” shanks)? I have a couple Kutzall burrs…they’re okay…would like to try something else.

Thanks all…

9 replies so far

View jap's profile


1251 posts in 2053 days

#1 posted 05-28-2013 01:47 PM

I would not put a 6mm bit in a 1/4” collet but, If you have a 1/2” collet router you could use one of these bushings their cheap too.,46168,46180,30126

-- Joel

View henigail's profile


12 posts in 1835 days

#2 posted 05-28-2013 03:38 PM

Thanks for the response, jap, but the rotary rasp will be used in my die grinder, which has a 1/4” collet. I’m looking for either a source for rotary rasps of Auriou quality with 1/4” shanks, or (preferably) a collet for the grinder that can accept 6mm shanks.

View Shawn Masterson's profile

Shawn Masterson

1325 posts in 1947 days

#3 posted 05-29-2013 02:37 AM

I wouldn’t blink an eye. the collet is tapered it will snug right down. I would be cautious knowing that it may make the collet smaller, so putting in a 1/4” bit may be a challenge. I would go to HF and get one of there throw away mini die grinders. if you look at the collet the tighter you make it the harder it squeezes the bit. Mine didn’t come with the 1/8” collet, but if you were that scared you could have the 1/8” collet machined out to 6mm.

View Loren's profile


10394 posts in 3646 days

#4 posted 05-29-2013 03:16 AM

It may fit. Even 1/4” bits have quite some variance
in size and remember, routers go at 24,000 rpm.

I have had router bits fall out of collets several times. It
is not scary, really. It just messes up the work. The bit
stops spinning when it falls out – it does not become
a helicopter-like projectile.

View unbob's profile


810 posts in 1902 days

#5 posted 05-29-2013 05:57 AM

There are quality ” air”die grinders that use Erickson double angle collets that have a full 1/32” range, among those brands are Dotco and Cleco. Those DA collets are designed for the wide range of grip, available in sizes by 1/64s and metric.
Most other collets are for a specific size only, those collets can break,spring out of shape, or usually not run true if the tool shank is off size.
There is another option for many routers on the aftermarket, with conversion chucks to ER style collets.
The ER style collets are a standard in metal working, and much better then the odd shaped collets installed on routers.
Where as , a Bosch collet does not fit a Porter Cable. Maybe at some point the wood working industry will move to a standard collet.

Sometimes, a tool pulled out of a collet at high RPMs can fling out with considerable force. Best to avoid that problem.

View crank49's profile


4030 posts in 2969 days

#6 posted 05-29-2013 04:45 PM

It may work if the collet has enough range, or it may still be loose after the collet has bottomed out. I have gotten around this problem by wrapping a thin strip of shim stock around the shank and then inserting in the collet. Have used this method in tools spinning at 32000 rpm and had no problem.

View robscastle's profile


5000 posts in 2203 days

#7 posted 03-12-2016 08:07 AM

I have some 6mm ruter bits and I found they do not fit in a 1/4 or 6.4mm collet sucessfully.

Dangerous to say the least. (Say no more)

So they got shelved and I bought 2×6mm to 1/2 ” collets on ebay, I am awaiting their arrival.

-- Regards Rob

View rwe2156's profile


2925 posts in 1479 days

#8 posted 03-12-2016 02:20 PM

1/4” = 6.35mm.

I would try some shimstock.

-- Everything is a prototype thats why its one of a kind!!

View MrRon's profile


4769 posts in 3242 days

#9 posted 03-12-2016 05:18 PM

Absolutely not.

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