On Thursday 28 July 2016 16:32:48 Gene Heskett wrote: > On Thursday 28 July 2016 15:29:39 andy pugh wrote: > > On 28 July 2016 at 20:10, Gene Heskett <[email protected]> wrote: > > > So I am thinking it should do a prep operation to cut the taper > > > first, ding it with a fairly fine feed so as to leave a fairly > > > smooth surface to start the threading operation on. > > > > If it is a full-form threading tool then the initial surface finish > > is relatively unimportant. > > Single tooth, fully formed for some arbitrary thread I've never been > made privy too, so I'm doing SWAG's, Andy. I might be able to define > the flat on the tip if I had a calibrated microscope. But I don't. > From looking at it, I get the impression it would clean the tops of > the cut thread if driven to anything coarser than a 2mm pitch. IMO > driving it deep enough to clean the tops of the thread would be > abusive, so I use it for finer stuffs. > > Cheers, Gene Heskett
After dinner I brought the tool and my best magnifying lens in to get a good look at the internal threader. There does appear to be a flat on the tip, perhaps a thou wide. And I'd put its max pitch at 1.25mm's after a closer look. Anything over and I can see in my mind, the offcut chips running into each other as they are peeled away by the differing edge angles. That does leave a bad finish in my experience so far. My inclination, if I want the smoothest finish, is to use the "spring passes" to widen the bottom of the thread by sweeping it fwd a few thou to make the P/6 width flat at inner, then back to the start to shave the burrs for a last pass, and if boring an internal, to sweep it fwd enough to make the bottom of the groove a P/4 flat, and again come back to the starting z for a last pass to shave off any burrs. To do that correctly is likely beyond the ability of the little monster to unless I replace the front gib at least with a tapered gib so I can stop the slight twisting on the ways that the carriage now does at a direction reversal because the weight of the motor plus gib drag on the rear bed lip is too much for the front gib to control. 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> ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
