[Hallicrafters] knob retaining screws

[Dick Blaney]

Those are Bristol socket headed set screws.  Sometimes called "Spline 
Socket" screws.  Many Hallicrafters, Collins and US Military equipment use 
these screws.  They are much finer and more secure than to Hex or Allen 
screws and more sturdy than slotted.  Slotted tends to "burr" up the slots, 
and Hex sockets are prone to splitting longitudinally.  Spline sockets are 
not subject to either, since any radial force is in line with the 
circumference of the screw threads.  I believe that both Collins and 
Hallicrafters tended to use this pattern of set screw because the Military 
demanded it and both were heavily involved in Military contracts.  Wrenches 
can be obtained from several mail order sources, but the last I bought, (I 
tend to misplace things like this), I did a search for "Bristol Wrenches" on 
eBay, and found that a fellow in one of the Carolinas sells in a set quite 
reasonably.  Hope this helps.
Dick, WB8MHE

----- Original Message ----- 
From: "Douglas" <iluznst at yahoo.com>
To: <hallicrafters at mailman.qth.net>
Sent: Thursday, October 04, 2007 12:37 PM
Subject: [Hallicrafters] knob retaining screws


> Hi,
>
> I've encountered some set/grub screws holding knobs on
> that are not allen or slotted screw, they seem to be 4
> sided. What type are they and where is a good place to
> find a wrench to remove them?
>
> Douglas
>
>
>
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