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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
