Question about tool bits.

[Nelson_2008]

Hello,

Basically I want to put a series of 1/8" wide x 1/8" deep grooves in some UHMW polyethylene round stock, but the set screws in my QCTP tool holder aren't long enough to hold a 1/8" square tool bit.

So I'm wondering, does anyone see anything wrong with using a square 1/4" HSS tool bit as a shim, underneath the 1/8" tool bit, so that the set screws in the tool holder will tighten down on it?

Regards,
Nelson_2008

[sti2011]

Having to shim lathe tools up or cutting them down to get them on center, above or below centerline is, as old a process as lathes themselves! Shim away as neccessary............Even the best quality CNC tooling requires different seats (READ SHIMS) to get tools of different tool tip rads "on center"

[Nelson_2008]

Thanks for the reply.

One detail I forgot to mention is that the 1/8" tool bit is not in contact with the wall of the tool holder, but only with the 1/4" tool bit below it (which is against the wall of the tool holder), and two set screws above it.

I don't know whether contact with the wall of the tool holder is generally important or not, but for the plunge cutting I was planning to do, I hope it's not an issue.

[sti2011]

It's only relatively in-expensive plastic, try it on a piece of scrap and see if chips fly! BTW a shop vac will keep chips from wrapping if you keep the tool cutting a consistant chip and the vac close enough to drag it in the hose. I have cut some really stringy plastic at some really high, feed and speeds, so long as you can get the "string" started into the vacuum.

[kawazuki]

Why not just grind a 1/8" width end on to a 1/4" / 3/8" blank similar to a parting off bit?
Or am I being dense?