[EvanVH]

It all has to do with knifes and nuts?????




Evan

[BobWarfield]

They're not quite the same, Phil, though they may be close enough as not to matter:

R8 = 16 degrees 51 minutes.
CAT, BT, NMTB = 16 degrees 35 minutes 40 seconds

At some point, any taper may require a little extra effort to release. But, CAT, BT, and NMTB all release more reliably than R8.

It's a moot point, though. The only application where it matters is with an ATC, and all of these taper styles will employ some positive pressure on the toolholder to make sure it releases. In other words, an air cylinder is driving down the drawbar whether that is threaded or engaging a retention knob.

Cheers,

BW

[Runner4404spd]

Bob, all the holders have a tendency to stick. i even had a cat 40 holder stick in my fadal spindle and i know thats alot better machined and assembled than any chinese mill. the real difference in the sticking i think comes from the differences in thermal expansion of the materials used. i've had R-8 collets stick and need some tapping and i've had the solid holders come right out.

really it comes down to the application and ultimately i think the NMTB 30 has more surface area in contact with the spindle. is this better? maybe, it also seems to have more of the holder withing the area where the bearings are.