Aha! I'm looking for six to ten of the 4-40 x 1/2 inch Bristol socket head cap screws for the BFO and BW shaft clamps. One square nut (if available) would be helpful as well. If not, I'm sure there would be Allen head screws at my local hardware store.
But What didn't work for the ham I got his from was a mix of slotted and Phillips screws -- the heads wore out quickly. -Fred ------ Original Message ------ Received: Tue, 16 Jun 2026 03:32:34 AM GMT From: robert meadows via R-390 <[email protected]> To: R390A <[email protected]>, Tisha Hayes <[email protected]> Subject: Re: [R-390] Weird looking set screws Miss Tisha,Good to see you are still active. I thought that everyone knew about Bristol spline.... I have had a set since about 1961.CheersR On Monday, June 15, 2026 at 11:14:00 PM EDT, Tisha Hayes via R-390 <[email protected]> wrote: The R-390/ 390A use set-screws that are designed for a much higher torque application. It is known as a "Bristol-Spline" screw head. It may look like a hex or a little like a TORX but the internals are all right-angles instead of triangular or hexagonal faces. The old Xcelite tool-set included Bristol-Spline bits, back in the day most people had no idea what to do with the Bristol Spline bits. The reason for Bristol-Spline is that when tightened it will not cam-out (strip) like a hex bit will. *Ms. Tisha Hayes, AA4HA* ______________________________________________________________ R-390 mailing list Home: http://mailman.qth.net/mailman/listinfo/r-390 Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ R-390 mailing list Home: http://mailman.qth.net/mailman/listinfo/r-390 Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ R-390 mailing list Home: http://mailman.qth.net/mailman/listinfo/r-390 Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
