ER 11 run out using .25" bits

So I hardly ever use quarter inch bits but I do have occasional need for them and I have noticed that the ER11 system doesn’t handle it very well. It won’t fit into a 6 mm college but I keep getting slop and about 50thu of run out I need to tap out. I also don’t get the “click” that means it’s locked in.

Do I just have shity import collets, or is there a metric to imperial conversation thing going on? At 6.35mm it’s over the normal 0.5mm collapse for the collets but way to big to fit a 6mm.

I would recommend buying a 1/4" ER-11 collet. I believe I read here that the 6mm collet does not have the tolerance to properly hold a 1/4" bit. I use a 1/4" bit in my ER-11 collet frequently without issue.

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Please try a proper 6.35mm collet such as:

Note that for a Nomad 1/4" endmills should only be used with softer materials such as wax or Renshape.

I had the same issue with 6mm collets combined with 6mm shank endmills, even high-quality collets (rated to less than 5 micrometer runout). No issues with 3mm shank endmills.

I’m kinda an idiot when it comes to this stuff but I think the problem is that ER11 is just too small to securely and accurately hold a 6mm shank endmill. 3mm shank endmills are usually ~40mm long while 6mm shank endmills are usually ~60-70mm long. The extra stickout “magnifies” any runout (I think, maybe the collet rating takes this into account).

I’ve bought an ER16 collet holder/shank that should fit in the Nomad spindle and I’m going to try it out and see if ER16 collets work better. They’re deeper, not just wider, so they’ll reduce the stickout.

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Er11 can actually hold up to 7.5mm. You’ll get runnout problems if you try to go bigger than the recommended range, the collet wont seat properly. The number on the collet is the maximum size allowed.

I have seen some cheaper er collets interfere with the lip on the nut and effect seating also. Cheaper also usually means more TIR.

These Maritools have a 0.0003 TIR