On Monday 20 March 2017 10:19:49 andy pugh wrote: > On 20 March 2017 at 14:14, Dave Caroline <dave.thearchiv...@gmail.com> wrote: > > probably easiest to EDM the square > > I would need to find space for the EDM machine.
I do EDM on my little HF mill Andy. But I connect the EDN power wires so the currant doesn't have to flow thru the spindle bearings. Most of the time I either use a small wire, which is a pain keeping it on target as it burns away, or for bigger holes a brass tube, both spinning so theres enough jiggle to keep it from sticking. Or the last time, I mounted a 3" diameter brass disk about .0325" thick, and used it as a saw blade to cut a bored hole, already taper threaded, think pipe thread but 50 tpi, so I had 6 metal petals the nut could squeeze down onto a piece of ball screw. It might as well be welded, and that was the idea. Crossfeed screw for this old Sheldon I'm converting. The off intended use of the end tapering of the g76 was used for that. Discussed on this list at the time. For this, I'd mill the shape on a carbon stick long enough you could afford the length loss when you face the end square to get fresh, sharp corners, and drill a central hole so you could pump fresh distilled/deionized water into the gap for debris flushing. The central post left by the dielectric flushing hole can be milled off easily enough when the needed depth has been reached. A smaller, but still square carbon rod could also be driven in a square pattern in the xy at a high enough rate to circulate the water for debris control, while descending a few microns per loop would also work and wouldn't leave the hole sticking up. Turn off path blending of course. I've not tried that on my small mill as its still doing SW stepping at about a 8 to 10 ipm rate, and probably not fast enough to circulate the water well. I need to get off my duff and put a 5i25 card in it. And another 12 to 15 volts of motor voltage so it can move. Shoemakers kids comes to mind. :( Tomp can advise how much power you would need to get a decent erosion rate. The most I've ever used in a purely rc circuit was 80 volts and about 3 amps into some 1/4" OD brass tubing to drill some holes in an Avanti table saw blade, so I could mount it to a rotary table and sharpen it. 10 uf discharge cap, a huge paper/oil transmitter spare, and 2 50 ohm 200 watt r's in parallel for an rc discharge. Noisy, you could hear it for blocks & I put my -30db shooting muffs on. But it also made those holes in the saw blade in about 15 minutes a hole. 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
