Phil brings up an interesting point. Since the thread helix is determined by motion of the z-axis and the thread form is determined by the spinning of the tool (which is not coordinated with any other motion), there is a real possibility that the resulting thread will not be perfectly formed. The issue is: what is the best diameter for the thread-mill tool. An infinitely small diameter tool will probably form a perfect thread, but will have no strength to cut the threads. A tool diameter that approaches the minor diameter of the thread will form the worst threads.
Other issues with thread milling: 1)The thread mill tool will not follow the pre-drilled hole as will a tap. 2)Getting the correct pitch diameter from a thread mill is a trial and error routine. I have a friend running a commercial CNC machine shop and he uses thread mills only for difficult jobs, such as camera lens threads which was mentioned earlier. But, he still must buy a thread gage if he is not making both mating parts because of the tolerances with thread milling. Anyway, I really enjoyed this thread (excuse the pun) with a lot of thoughtful people contributing. Glenn -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Andre' Blanchard Sent: Wednesday, May 21, 2008 5:19 AM To: Enhanced Machine Controller (EMC) Subject: Re: [Emc-users] Thread Milling At 04:35 AM 5/21/2008, you wrote: >I think I have a grasp of how this thing works now. My only question >left is, if the "teeth" are in rings, and there are multiple rings (and >assuming the thread mill is spinning at that same time as the x and y >axes are moving), how does the tool keep from munging the threads that >are already cut if there is no "screw" ramp to them? From the looks of >the thread mill in the picture, the thread mill's "rings" all seem to >be parallel with each other, and have no screw ramp. > >Mark When using the thread mill the "screw ramp" comes from doing a linear Z move while doing the circular move in the X,Y plane. Thread mills tend to have extreme amounts of relief angle on the cutting edge to avoid rubbing in the tight spots they are used in. Some cutters have teeth that look a lot like the top half of a birds beak (hawks or owls). That form relief is one reason they are so expensive. __________ Andre' B. Clear Lake, Wi. ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
