Rotozips use a 5.5 amp motor and spin to 30,000 rpm. Very similar to a high end die grinder.

Where do you buy the grinding barrels and carbide cutters?

 

Theres a couple of 'bumps' in the housing that you can't do much with due to the outside bolts embossing. Let me measure it real quick.

 

OK, at the ID of the DP end, it measures 2.242 for about 1 inch in. Then it opens up slightly and 'belly's out through the 'convergence' area to a little larger 2.488 one direction and more (due to the waste gate blending) and then blends back to the original 2.513. The DP material thickness is .168 for about 3/4 inch. Inside further, it's difficult to tell due to the shape.

 

If there is reasonable wall thickness, sounds like there is some room for opening up the DP end. Guess I'll go track down some carbide cutters. Thanks again.

 

I get the cutters at a local hardware/automotive store. Make sure they're carbide. Lowes carries a few sanding barrels. My main concern for using the rotozip was the 1/4" shaft and heavy duty bearings of heavy side load pressure. The Makita is actually 25000 rpm, but I think not nearly 5.5 amps. I also use CP air tools, but I hate dealing with the hose and compressor noise. Good luck. If you need anything else, let me know.