On Wednesday 07 March 2018 06:42:26 andy pugh wrote: > On 7 March 2018 at 04:05, Gene Heskett <ghesk...@shentel.net> wrote: > > So the only way is to buy R8's with square bores, > > I don't think that is the only way at all. > > You could make solid ER32 "collets" with grub screws in the end. > (getting the extractor flange right would be a challenge). > Bored true they would hold the tap true, with drive from the grub > screws on the square. > Needs one per tap size, but it's an easy CNC turning job. > I think the 3/4" brass rod idea, bored thru for each tap, with grub screws to grab the square butt, and a key slot cut in a 3/4" R8 to lock it to a cap screw seated in the side of the 3/4" brass rod, one per tap size, might be the best idea.
> I recently (and accidentally) bought a pair of floating tap holders. > There is no reason that those would not work for rigid tapping, and > they add a bit of relaxation to the process in the event of a problem. > Those take a DA collet and have a pair of grub-screws to grip the > flat. > > ER collets specifically for tapping exist (with a square in the back) > https://www.ebay.com/itm/Techniks-1-2-ER25-Rigid-Tap-Collet/1221226735 >10 Price is scary, and still leaves the collet free to slip. I think I'd rather sacrifice an R8 by grinding a key slot into it for a cap screw in the side of a brass tap holder, to lock it from slipping in the R8, and make a dozen or more, about an inch long. Like you said, once the code is written, it can make as many as I have brass on hand. I now have the Sheldons bent spindle corrected, and an ER-40 kit that sits in the shop-made 5C adapter, and running within a thou several inches away from its collet. I'll have to measure, but I believe it can pass a 3/4" rod, length arbitrary to about 3 feet as theres a storage shelf to the left of the lathe it will hit. If I add the rear spider I made, I should be able to maintain it pretty true. Now, to find the 3/4" brass in 3 foot hunks. > You could add a pair of drive grub-screws to a standard round R8 > collet. You might need to soften it off to allow tapping, though. > At which point you might as well make your own, again it's a simple > turning job. You wouldn't need to heat treat for your volume of work. > It would not need to be a split collet. Bored for the tap diameter and > relying on screws for grip and retention it ought to be fine. -- 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
