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. I have a parting tool that I have threaded several times on a manual South Bend Big 10 (and now a Monarch 10EE)
On Mon, Jul 23, 2012 at 7:52 AM, Gene Heskett <[email protected]> wrote: > To Andy & Steve; > > I made another of the dual thread screws yesterday, and can report that it > seems to work well. However it seems that I must have a flexibility > problem in using a cutoff knife sharpened with a 60 degree V and a slight > (10 degree?) hook though. Or it doesn't have sufficient 'heel' clearance > and is being pushed until there is a supporting thread on both sides of the > tooth. > > The entrance thread, even though the starting point of the fwd cutting > stroke is well off the end of the workpiece, I am getting a 'first thread > is bigger' effect, about 15 thou bigger TBE! This was very obvious when I > cut the 10-32 thread, slightly less so when I cut the 7mmx1.00, but > required I trim about 2/3rds of the first thread off with a dremel diamond > wheel. > > Two things became obvious, one being that I have no way to actually measure > the pitch diameter of a thread in progress, and because of the fat end > thread syndrome, it doesn't seem practical to try and use the matching > threading die as an "am I done" test gage. That, and the die I have seems > to have several thou of thread clearance, so a hole tapped with the tap, is > a pretty sloppy fit on a screw made by the matching die. I like my threads > to fit better than that. > > How much of a heel clearance angle do you folks use when sharpening a > single tooth, and how much 'hook' on the top face? > > I want to make a jig for this as setting up the rotary table on the mill, > and tipping it fwd to get the heel clearance angle seems to work but is a > setup PIMA due to the tables motor hitting the heads gearbox. > > 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! > Civilization is the limitless multiplication of unnecessary necessities. > -- Mark Twain > > ------------------------------------------------------------------------------ > 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 > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
