Yes, those Bristol-Spline screws are almost unreasonably durable; You can torque them to incredible levels and you would almost be certain that the screw would shear off. The black-oxide ones do seem tougher.
Torx would be a good replacement, maybe not as high of a torque-out rating but probably more than enough for the application in a radio. About 15 years ago I bought up a bunch of the shaft-collars and Bristol-Spline screws from FairRadio and I know that I received them. I used them on two restorations where the hardware was broken/missing. For the life of me I cannot find any of the ones I thought I had left. If someone had been around during the St. Juliens Massacre (when so many R-390/ 390a's were left to rot) that would of been an excellent source for an unlimited amount of impossible to find hardware (along with the mini-BNC's, connectors, plugs, oscillator modules, crystals and slug racks). *Ms. Tisha Hayes, AA4HA* On Tue, Jun 16, 2026 at 12:28 PM Renee K6FSB <[email protected]> wrote: > might i suggest next best thing to Bristol spline would be torx which are > not too difficult to obtain and much less chance of cam-out than allen. > Renée, K6FSB > > > On 6/16/26 10:13 AM, Jacques Fortin via R-390 wrote: > > Hi Fred, > IF EVER you found a valid source for the Bristol ones, let us know ! > Allen head ones are more easy to find... > Use the largest head recess size (3/32"). > But resist the temptation to buy the Stainless Steel ones: these are less > "tough" than the black oxide coated steel ones... > And for the square nuts... I already "made" some from standard 1/4" hex > nuts. > File or grind those on three sides. I prefer brass to the steel ones > however... > > 73, Jacques, VE2JFE in Montreal > > 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 > > ______________________________________________________________ > R-390 mailing list > Home: http://mailman.qth.net/mailman/listinfo/r-390 > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] <[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
