Actually. I think that is why spline screws fail, they are torqued, as you say,
to incredible levels. In my experience, the only time the spline screw fails
to hold the clamp in place is because either the shank or spline head has
failed. Then there are those clamps and knobs that are still holding as they
should but the spline head is now so buggered that you cannot loosen it.
There is no credible reason that requires the spline machine screw to see such
heavy handed abuse, IMHO.Jim
Logic is a systematic method of coming to the wrong conclusion with confidence.
Murphy
On Tuesday, June 16, 2026 at 12:38:48 PM CDT, Tisha Hayes via R-390
<[email protected]> wrote:
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
______________________________________________________________
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
