On Tuesday 24 July 2012 06:30:42 mark center did opine: > I use 0 to 5 degree rake and 2 to 3 degrees absolute flank clearance. > The compound angle, viewed orthogonal to side view, is about 10 to 15 > degrees. The spiral effect (lead angle) causes entering side to be > more acute than exit. Nothing is really terribly critical as long as a > cutting flank does not rub against either side of the thread flank. > Ridiculously acute appearing tool angles will cause less problems than > angles that would appear correct for turning, they just wear faster. > You might only be able to thread ten or fifteen parts before you need > to resharpen. The lead angle is a function of lead, diameter, and > whether internal/external.
Rather than make a jig, since I didn't really know what I was doing yet, I just tipped my vise up 60 degrees and clamped it into the vice at about 15 degrees to the left on the right side of it, with a 1.5" dremel diamond wheel and arbor in a drill chuck in the spindle, turning about 2000 revs. That took me about an hours worth of sweeping it back and forth, lowering the z about a thou per pass to get rid of the belly and bring the shine all the way to the edge, and when I did, I found it was sensitive to the wheels direction of rotation, leaving a shiny line at the cutting edge that would not wipe or blow away if the wheel was turning to approach the edge, but which was almost instantly removed if I reversed the spindle so the diamond was traveling upwards toward the edge. Then I turned it over but set the left face at about 20 degrees, (pitch angle SWAG) which again started polishing the lower side first, and I've lowered z an additional 20 thou since. When I gave up well after dark last night, with about 30 thou to go to get it up to the cutting edge, meaning another 3 to 6 thou down at the spindle. Apparently my attempts to sharpen by hand had left it effectively with zero heel clearance on the left, cutting edge. Quite a belly on the side I am having to remove. Because the threads I was cutting are relatively fine pitched, I haven't tried to form a round nose on the tool other than making a just visible shiny spot on the end, not more than a couple thou wide with a hard arkansas stone. The first thread I cut with it was beautiful, the last were pretty rough feeling but worked. > I have a parting tool that I have threaded several times on a manual > South Bend Big 10 (and now a Monarch 10EE) I've not considered buying an insertable tool yet, most of the tool shanks are too big for this machine, and the inserts are sold by the karat. But it would be nice if there was a side of the tool clamp for the cutoff tool, most holders offer little or no sideways deflection restraint, with this a2z's wedge style clamp being particularly non-impressive in that regard. More bad weather today, it was 76 at 6 AM, with severe afternoon thunderstorms predicted. The only advantage of the heat to me is a lighter weight sock to keep my diabetic feet from feeling like they are freezing. I hope it doesn't replay 3 weeks ago, there are still some folks in WV without power. And the state P.U.C. is all over the electrical folks because of it. Thank you Mark. Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> is up! Eschew obfuscation. ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
