Collets and end mills


My router (Katsu) has a 1/4 collet (actually measures 6mm).

Most talk on here is of 1/8 end mills. I can get end mills with 1/4" shanks and 1/8" cutters easily enough, but I’m wondering if I’ll face clearance issues.

Is a collet reduction sleeve to 1/8" recommended?


I’m also interested in hearing the answer to this. I also have a 1/4 collet and am looking for some smaller bits to use and these seem to be more readily available in the smaller collet sizes.

It’s better to use the collet for the bit you have. If it’s for 6mm bits, I wouldn’t even use it with 1/4" bits. I certainly wouldn’t use it with a 1/4" to 1/8" adaptor if it’s meant for 6mm. I don’t know about 6mm to 1/8" adaptors, but any wobble would make a real mess when you are 3/4" into the material already, and moving at speed, depending on the already cleared material.

Also, I don’t know about the projects you plan on doing, but the riskiest part is going to be at the end when it’s at the deepest. I value my time and the material enough that I would think twice about shortchanging anything w.r.t. the collet.

I would either find another collet or find bits that are meant for the collet you have. w.r.t. clearance, the bits have a cutting width, a shaft width, and a max cut depth. I have been cutting beyond the max cut depth with my 1/8" bits, but I don’t know if I am supposed to. You should be able to find longer bits if you’re wanting to cut more than 3/4" into the material, or whatever. You’ll need a little more clearance than the material thickness, just for tolerances in Z. Having the collet rub on the material will cause a lot of friction, and is a good source of fire.

Whatever bit you use, you’ll specify the cut width in your CAM software, so there’s no reason you can’t use a 6mm bit either. The 3mm or 1/8" bits will get into corners better, and they can cut a little faster and they are more robust than the 1/16" bits.

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Hopefully you can find a new collet. I have not tried a sleeve but it does not sound like a good idea. You should easily be able to find the correct shank size on any diameter tool that is that size or smaller. The advantage to a smaller collet is the smaller tools tend to be cheaper that a large shank and small bit.

I sell smaller collets for the dewalt and they have several sizes available for about the cost of 1 bit. I get them from the Elaire Corporation, maybe they have one for your tool.

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I’ve ordered a few 6mm shank end mills with 3mm cutters for now.

Yes it seems the Elair lead is a good one.

All the 1/8" collets I’ve seen elsewhere seem to be for the die grinders (rotary tools). Models such as 906, GD0600 and GD0601.

Elair have one that supports the RT700C. I’m lead to believe these should also work on the Katsu.

$24 for the 1/8". I couldn’t get their basket to work, will update the thread once I know shipping to UK.

Imperial collet part number for these is: 763637-1. Does start to look like Elair are the only ones doing 1/8" versions (wow).

Looks worth it in the long run because as has been said, the 1/8" stuff is cheaper - looks about half the price at first glance than 6mm shank.

Yeah they have a solid product, I am pretty amazed at the quality. I just ordered 50 more this morning. I can tell you the “bulk” discount is very minimal so I think they generally just sell one or two at a time and have a small/reasonable markup. I have nothing but good things to say about them so far. You never know though, I still use some of the very first cutters I bought they do last a long time if you don’t go running into screws and clamps so it may or may not be worth it for you. Just get 3 good endmills and that might last a very long time.

£32 to the UK shipped. The Katsu was £35 :\

Might be the excuse I need to save for a nice quiet spindle, then I can chuck the Katsu on the LowRider once she’s made.

More reading about choice of spinning machine.

I’ve seen some tear-downs now of Chinese spindles, and the manufacturing tolerance and runout of these machines has been called into question for me now.

I am starting to conclude that the quiet thing is a non-issue, because people report that the noise is similar between trim routers and spindles while cutting is taking place.

I learned that the Elair collets were manufactured in response to user demand from hobby CNC makers, and given their reputation for engineering, and the reported runout on the Katsu being low, I think I will probably invest.

Also received the 6mm shank/3mm cutter bits. I haven’t seen the max depth data for these, but there is only about 15mm of usable tool if that because of the transition from shank to cutter.

I was running the LowRider again today, the 611 is a lot more quiet than the 660. I can honestly say the sound of the spindle means nothing. I had the vac and the 611 going and it is as loud as a shop vac…when the bit hits the wood, that is by far the only thing you can hear. I will upload the little video I did. I think this might ends the sound issue for most people.

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Is there a mount for the 611 for the mpcnc?

I am sure there is but I have not made one for the MPCNC, it is too large and heavy. I have it on the LowRider CNC.