Glenn R. Edwards wrote: > Jon, > I hope it doesn't appear as though I am jostling you for the final word, > however you pointed out a major difference between us hobbyists and > professionals. A professional must deliver a part in spec 100% of the time > ( six sigma- don't get me started...) no matter if the part was cut in the > cold morning or during a hot afternoon, if the part was mounted at the > center of the table or if mounted near the edge, if the machine was being > run by your best operator or the guy you hired yesterday. > > A tap can wear, but so can a thread mill cutter and probably faster. > However, thread milling introduces two additional tolerances that tapping > does not. Each of those tolerances can (and eventually will) produce an > unacceptable thread. A loose fitting thread can have a LOT less pull-out > strength than a properly formed thread. And, you might not be aware of a > loose thread unless you have a GO NO-GO gage. In my day job, I want tapped > holes from the machine shop (In fact, I am getting quite accustomed to > roll-tapping and the superior strength thread it produces). During the > weekend, I will enjoy making my own threaded holes with a thread mill. Yup, I have to say I do not do aerospace work, or much where a mechanical failure would endanger life or limb. And, I am not a job shop where all my parts wind up passing under the scrutiny of my customer's incoming parts inspector.
On the other hand, I buy a lot of stuff that is SUPPOSED to be tested, and I have a little pill bottle full of screws with no threads or no recess in the head, and such like. My guess is that thread milling with a worn cutter will result in an under-size internal thread or an oversize external one, in either case the parts can't be assembled, rather than a too-loose thread. Jon ------------------------------------------------------------------------- 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
