# 3mm bits?



## grobinson6000 (Jun 22, 2010)

Hello,

I'm relatively new to routing, but have inherited some very small carbide spiral bits for doing fine work (slots, signs, inlay) in plastics and particle board. They're a tiny 2mm diameter, but oddly have a *3mm* shank (I swear, they're not 1/8" like everything else. I'm a qualified mechanical engineer, apparently, so I should be able to measure good by now).

I'm looking to buy a new smallish router (our ancient one has of course seized up with decades of disuse), and was wondering whether anyone knows much about using a 3mm shank bit: is it close enough to a 1/8" bit to be safe in a 1/8" collet or sleeve? Or should I be trawling Google for a mythical unicorn/thylacine/1/4"-3mm sleeve?

Thanks,
George


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## jlord (Nov 16, 2009)

Hi George,
Are you sure those bits aren't for use in a chuck like on a mill or something?


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## harrysin (Jan 15, 2007)

grobinson6000 said:


> Hello,
> 
> I'm relatively new to routing, but have inherited some very small carbide spiral bits for doing fine work (slots, signs, inlay) in plastics and particle board. They're a tiny 2mm diameter, but oddly have a *3mm* shank (I swear, they're not 1/8" like everything else. I'm a qualified mechanical engineer, apparently, so I should be able to measure good by now).
> 
> ...


George, no way would I attempt to use a 3mm shank into a 1/8" collet, which, as you know is 3.1750mm. As you are a mechanical engineer I'm sure that you can do what I would do, and that is turn-up a sleeve for a standard 1/4" or 1/2" router.


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## CanuckGal (Nov 26, 2008)

They may be for use in a Dremel type tool. In Canada Canadian Tire sells their own brand dremel tools (Mastercraft) and also a cheaper brand called Jobmate. I have run into issues where some bits and collets are not interchangeable between these tools and Dremel branded ones. I don't know where you are located bit those bits might have been made for an off branded dremel tool.


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## istracpsboss (Sep 14, 2008)

They sound to me like something used for machining printed circuit boards in CNC machinery. They'll snap like a carrot unless you are very careful.
I was lucky yesterday using a 4mm bit but I did the cuts in numerous stages.

Cheers

Peter


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## BigJimAK (Mar 13, 2009)

Ahh... the old "Metric vs. Imperial" trick! (c) 1966 Maxwell Smart


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