die grinder can't be both 1/4 inch & 6mm?

[gaaah]

Shouldn't a die grinder with a 1/4" collet be able to grip 6mm bits?   Gee whiz, the difference in diameter is only 0.014.  Yet only the Dynabrade grinder advertises that it can take both (and I can't use that because it's pneumatic, not electric).   I have an old 2nd hand DeWalt 887 with a pretty worn collet.    I got out in the field today and ran into a wall because it wouldn't grip a 6mm bit.   Surprised.   I don't know whether it's because the collet is shot or that it never could even when new.

[jeffmcmillan]

Welcome to the forum.

 

I wish collets had a wider range, but that 5% difference is not trivial for fitting something in a collet.  That said, if you really tighten it down I'd expect it to grip a 6mm bit passably so the collet is probably shot.  Check if the gaps cut into the collet are closing completely and you can file them wider to fit smaller bits if needed.  too much and bits will start to wobble though.

[gaaah]

OK, here's how I fixed it:   There's this screw-on cap that presses the collet into a cone shaped void in the spindle.  The cap was screwing all the way and bottoming out on the spindle, and the the collet showed there was plenty more space between it's kerfs to go.  So what I did was just insert a small washer between the cap and the collet so that the cap can push the collet further into the cone.   Works great, but I'll have the to put that little washer in a prescription bottle and in the case, otherwise I'd never remember it or find it.  

 

Also, I bought a new collet part, just to see if the problem isn't wear on the ID of the collet.

 

A thanks to Jeff for trying.

[gaaah]

Oh, and another thing I did was grease up the collet and spindle.

[jeffmcmillan]

You can probably file down wherever the collet nut (screw-on cap that presses the collet down) is bottoming out.  Engagement of more than a couple threads is usually irrelevant.