On Saturday 13 January 2018 17:27:39 tom-...@bgp.nu wrote: > Another question related to threading…. It is my understanding that > when cutting internal threads (or external threads) that after a > threading pass the tool should return to the driveline (“I”) in order > to retract for the next pass. But, as can be seen in the image below, > the various retraction paths (in blue) are not along a single > driveline. Why is that? > > https://www.dropbox.com/s/0ofspmm4pi8aw4f/g76i.jpeg?dl=0 > > -Tom
You might want to put a G64 p0.0005 in that code. This to restrict the TP's blending. You might, from the looks of that, want to cut the J back a ways, and of course Q gets reduced to the face angle of the acme, plus a fraction of a degree. It must not be allowed to ever cut on both cheeks of the tool as that will probably wedge it and break it. R probably at least 1.75. Maybe more. J and R interact to a surprisingly large degree. I usually do a std thread at Q=29.875. IIRC acme's face is only 15 degrees, check on that! and of course square, by the same token is Q=.25 Look at: <http://www.nookindustries.com/LinearLibraryItem/Acme_Screw_Thread_Form_Terms> and figure out, probably after consulting with the client, which of the 3 common acme forms nook mentions you are actually dealing with. And hope the tool you have can be persuaded to cut the form of choice. A case can be made for measureing quite a few times. J sets the depth of the initial cut, and R determines the cut depth regression as it gets deeper. But the language in our docs all assume a std 60 degree faced thread. But you are contemplating an acme, so thats a heavier cut on the flat face of the tool tip, so I'd reduce J to almost a scrape cut, 3, maybe 4 thou because that flat face cut is going to be as much material removed as a std thread at J=0.010 would be. You'll want to be cutting on the face, and the leading cheeks edge. Because J is smaller, the number of passes, which R will modify, not including the H passes will go up. But thats better than a broken tool because you used a familiar value for the J and its too much for the tool. K might need tweaked too after reading the above link. 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
