1/4" collet for CNC?

The documentation for the SM2 says that, “The supported diameters of the bits range from 0.5mm (0.020 inches) to 6.35mm (0.250 inches).” I’m carving grooves in cutting boards and would love to be able to use a 1/4" bit. Is there a larger collet I can get to accommodate this, or is there a place to get a 1/4" bit with a 1/8" shank?
If anyone has used a larger bit I would appreciate some help with this.

I’m considering trying the DeWalt 611 Precision Collet, but I’m having trouble finding the thread specs…

Pretty sure the CNC collets are ER11. You should be able to pick a collet up for 1/4" on ebay, amazon, ali, etc.

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You just need the appropriate sized er11 collets for the bits you want to use.
You can buy a set of various sizes on amazon or ebay for cheap.

-S

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I purchased a set of collets on Amazon similar to the image below. These ER11 collets range from 1 mm through 7 mm as well as 1/8" and 1/4". Each collet is supposed to have a 0.5 mm clamping range so in theory you can clamp any size between 1 mm and 7 mm. I find that some of these inexpensive collets can run-out more than specified making some drilling difficult. I also find that I primarily use the 1/8" collet supplied with the Snapmaker and the 1/4" collet I purchased here.

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A warning about cheap import collets: they’re not great for small diameters. For small sizes in a collet, you really want very low runout, the deviation of the center of the collet hole from the center of the collet holder body. It is not inexpensive to make low-runout collets, and the cheap ones online are no exception. If you’re roughing with a 6 mm cutter, fine, but don’t expect great results in small sizes.

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I got the whole ER11 set, but I’ve also only used the 1/4 and 1/8-inch collets. And Amazon sells just a 1/4-inch, which would have been a much cheaper way to go.

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I too found that I only use the 1/4" and a 4mm. I use the SM one for 1/8".
But it’s nice to have the others as the bit I use the 4 for I didn’t realize wasn’t an 1/8" shaft until I tried to tighten it down.
I’m mostly using the 1/4" for roughing but for final passes I’ve found it works well. Not sure if I got lucky, or by the time you factor in any the deflection and weaknesses of the SM it doesn’t really matter.

It might not be wise to assume that the SM is a high quality collet. I haven’t bothered to measure run out because in practice I’ve had no issues.

-S