Like so many things, there were good reasons for their introduction at the time they started. Of course, over time and with the introduction of "newer" threads, plus changes in technology, those reasons fade from view. At least it makes for some interest! lol http://www.alanstepney.info Alan Stepney's Model Engineering, steam, and workshop pages. ----- Original Message ----- From: "Chris Crosskey" <chris.crosskey@xxxxxxxxx> To: <modeleng@xxxxxxxxxxxxx> Sent: Wednesday, November 21, 2007 11:14 AM Subject: [modeleng] Re: Mystery thread I never cease to be amazed at some of the insane threadforms some people design in, I also try never to be without a supply of sensible grub screws and their relevant taps... chrisc MODEL ENGINEERING DISCUSSION LIST. To UNSUBSCRIBE from this list, send a blank email to, modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.