As always Harry, you comments are clear and enlightening. So I was OK to start 60° threads as long as I didn't go so deep as to get into the radiused root, crest issues ? And I have always wondered how some people got a degree (°) key on their keyboard and I did not. Now if I could just find the "248" key. All I've got is 0-9. Thanks again for you help on this issue.
royce (w) Harry Wade wrote: > At 10:52 AM 10/28/01 -0800, you wrote: > >I knew I could count on your formidable experience. > >royce > > Royce, > I do have some experience in a very narrow area but I don't know > everything by a long shot, and don't want to, but since I've struggled with > this very thing you describe I thought I'd chime in and I can shed even > further light on your comments to Trent. The ME thread form is as you > suspected not 60°, it's 55°, and while the thread angle itself isn't of > that much concern other characteristics of the thread form are. > ME and BA series threads have a radiused crest and root. U.S. > threads have straight crests and roots and these will foul the radii of BA > and ME threads. I discovered this when I bought a number of US equivalent > to ME series taps and dies from MSC from their "specials" taps list. They > have most of the common Imperial diameters in both 32 and 40 thread pitch > in HSS. "ME" means nothing to general industry in the U.S. so of course > they were all 60° Unified thread form with straight crests and roots. I > soon found that my British ME fittings would only screw in a few turns > before needing to be "forced" to be run home. Snug is OK, even tight is > OK, but when anything on a loco needs to be forced (except press fits of > course) something is very wrong. It finally dawned on me that the problem > was the thread forms and stopping mixing them solved the problem. > You could of course knock the crests off the Unified threads and > avoid fouling that way but IMHO there is little enough meat in a 40tpi > thread as it is. The MSC taps and dies didn't go to waste because on many > projects I make all mating parts myself so it doesn't matter what thread > system I use as long as I stay with one form. > Also, I have used keyboard entry Alt+248 to attach a "degree" sign to > the 60 and 55 above. I'd be curious to know how many people see a degree > sign ( ° ) and how many see something else. > > Cheers, > Harry
