On Sunday 01 April 2018 15:20:28 Chris Albertson wrote: > I'm still trying to figure out why you would need a key. End mills > don't spin inside R8 collets. The collet holds them so tight that > something breaks before the end mill spins. > The cutting torque on an end mill can't, or has never made it spin in the R8, but I have had then walk slowly out of the collet, cutting deeper and deeper as the operation proceeds. Usually undiscovered by moi before the mill packs full of hot alu and is broken by the feed in place for that cut, so it not only wrecks the part, it breaks a $15 to $25 tool.
Tapping a hole is a different horse entirely. With a 5/16" USS tap in a ER32 collet, collet tightened with 2 wrenches about 16" long, then the TTS adaptor seated in the R8, and the drawbolt pulled as tight as I can pull it with the 8mm end of a 80 mill long 8 and 10 mill OE wrench, I have had the TTS holder slip in the R8, run out of room to sink deeper into the R8, and litterally explode that 5/16" tap by crushing it lengthwise. I have got to put a stop to the slippage by keying it every step of the way. A longer wrench, on a bigger head on the drawbolt would help, but I have put enough torque on tightening the drawbolt that I can feel it stretching, and its not yet tight enough to lock the slippage. I've no damned clue why they put such a teeny 8mm square head on that bolt, or why tormach, when designing the TTS toolholder, didn't put a key pin in the thing. When I get this done, the same thing will get done to a 3/4" TTS, and the TTS holders get equipt with the keying bolt to stop that slippage. Walking out of the collet is a separate problem, and will likely not be affected by that. Only pulling the drawbolt with another ton of pressure might help that. And I seriously doubt the bolt can stand another rom > If you do cut the R8 collet I don't see how to get the end mill in the > correct orientation. I think you would need to make a much deeper > slot with end mill parallel to the R8 collet The keying screw I'm writing about is inserted in the cylindrical side of the 7/8" slug, and its head engages the slot cut into a petal of the R8 as shown in the scribbled drawing. It has no other purpose but to lock the slug so it cannot turn within the R8. The slug, once seated in the R8, will then be thru drilled for the shank diameter of the tap its being fitted to, and that hole will be drilled while its mounted into the spindle and the spindle driven, and therefore reasonably true. Once thats done, 2 more cross holes will be drilled from side to side, perhaps 3/8 to 5/8" above the face of the slug, passing thru the just drilled hole, and tapped for a suitably sized set screw in each of the now 4 holes so that the tap is gripped by the flats on all 4 faces of its rear end. Hopefully the brass is strong enough the screws won't strip, in which case I regroup and start making them out of decent steel. > > On Sun, Apr 1, 2018 at 11:36 AM, Gene Heskett <ghesk...@shentel.net> wrote: > > On Sunday 01 April 2018 11:15:39 Andy Pugh wrote: > >> > On 1 Apr 2018, at 16:01, Gene Heskett <ghesk...@shentel.net> > >> > wrote: > >> > > >> > But the thought has come to mind that for series production, I > >> > also need a jig to hold these R8's when they arrive in order to > >> > cut the slot in one leaf of 3 leaf design, to make that cut in > >> > the lip for the keying screw. I see a lot of similar gizmo's for > >> > 5C tooling, but haven't tripped over one made to do the same > >> > thing to an R8. > >> > >> The 5C ones are for holding a workpiece in a 5C collet, not for > >> holding a 5C collet. With both collet types you would need to grip > >> something in the collet in order to clamp up tight. > >> > >> R8 is meant for cutter holding. What would be the application of an > >> R8 Spin indexing fixture? > > > > Apparently my description has not been adequate to describe what I > > want, which is keying the tap holder slug into the R8 so that it > > cannot rotate within the keyless bore of an R8 tool holder. The half > > circle, or a little over a half circle, as pointed out in the > > attached scribble, is where I want to cut away so as to allow the > > head of a 4mm socket head screw to enter into the cutaway shown in > > the end of the R8 so as to key the "tap hat" slug to the R8, already > > keyed to the spindle by its pin and locking slot, removing yet > > another potential point of slippage to screw up a hole while rigid > > tapping it. > > > > Short of spending 6 months to learn how to run one of the cadcam gfx > > engines and make a professional drawing, its the best I can do on > > the back of an envelope. My water bill TBE. :) > > > > -- > > Cheers, Gene Heskett > > -- > > "There are four boxes to be used in defense of liberty: > > soap, ballot, jury, and ammo. Please use in that order." > > -Ed Howdershelt (Author) > > Genes Web page <http://geneslinuxbox.net:6309/gene> > > > > -------------------------------------------------------------------- > >---------- Check out the vibrant tech community on one of the world's > > most engaging tech sites, Slashdot.org! http://sdm.link/slashdot > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users -- Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
