I use a RotoZip for my CNC router which has been fine for most work I do.
I only use 1/8" and 1/4" shank tool bits and so I need both size collets.
The collets that come with the RotoZip are pretty lame.
I get decent, but not great clamping with the 1/8" shank bits and the 1/8" id collet.
The 1/4" shank bits and that collet wobble really bad unless I mess around clamping and reclamping the bits to try and get them to center properly.
I can get ok results eventually, but it's a PITA.
The problem looks to me, and I am not all that familiar with collets, that both ends of the RotoZip collets are shaped like a barrell.
They don't have the flat rear profile or the front flared out section like most collets I see.
I considered changing over to a Bosch Colt Router as my spindle, which looks to be a better tool than the RotoZip, but they only come with 1/4" collets and I would still have to get a 1/8" collet.
Can I have custom collets made for the RotoZip?
If so, I am guessing it's probably really expensive.
Any advice on how to improve the tool clamping precision on my RotoZip?
Been a while since I solved this issue but I ended up purchasing a Precise bits collet set for my Bosch Colt and I could not be happier
Link to precise bits
It's an awesome collet, the only complaint is that it can be a bit difficult to get the wrench lined up perfecly on the collet.
Sometimes it just drops into place, sometimes I struggle trying to get the teeth lined up.
Besides that, it blows away the stock Bosch Colt Collet.
I set up a page describing my conversion here
My CNC projects page