01-03-2013, 07:38 PM
(01-03-2013, 10:05 AM)ml_woy Wrote: The insert I am using is a TNMG-321
I.C. 3/8"
Thickness 1/8"
Radius: 1/64"
The top of my tool holder is 3/4" x 1.06" and I was planning on mounting two inserts back to back with a .125" wall in the center separating them. In that way I could use the tool to do inside and outside radius's.
Another forum member recommended the use of this fastener http://www.use-enco.com/CGI/INSRIT?PMAKA=250-1299
A negative rake insert like that should be using and eccentric screw in the middle and a top clamp to secure it, just as most negative rake insert toolholders would have. I suppose you'd be OK with a #6-32UN screw (nominal O.D. = .138") but only of you're very gentle with the cuts or have the 2 non-cutting corners of the insert capured to keep it from moving while taking a heavier cut. Looking at the screw recommended on Enco's site, I'd be wondering where to get an M2.2 x 0.45 tap for it and how much would the tap cost?
If I were making a ball cutter using an insert, I'd choose a VBGT331 or similar. That way I would mill the pocket with a 5º per side (10º included angle) cutter to mill the pocket, put the tapped hole in at a position .002" closer to the walls of the pocket so the screw woould pull it into the pocket snug (just like all commercially made holders do.)