As Tel said, British Standard Brass. Whitworth form, and used to be quite popular. Some of the BSB are (were) also listed as ME threads in some books. Alan Stepney http://www.alanstepney.info Model Engineering & steam engine information pages ----- Original Message ----- From: "TEL" <tel@xxxxxxxxxxx> To: <modeleng@xxxxxxxxxxxxx> Sent: Tuesday, December 26, 2006 12:34 AM Subject: [modeleng] Re: Mystery thread It's a standard Brass thread Harry - all 26 tpi. 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.