[ARC5] Removing knobs - verse two.

[Kenneth G. Gordon]

On 17 Nov 2019 at 11:08, Waldo Magnuson via ARC5 wrote:

> The set screw in the audio volume switch on a C-1254A control unit IS
> a Bristol set screw. The wrench fits tightly, I´ve used Blaster
> penetrating Oil but even with excessive torque the screw has not come
> loose. Any suggestions- heat/cold/drill? Skip W7WGM

Drilling won't work, since the set-screw is USUALLY hardened steel. Any attempt to drill will 
only damage the knob since the drill bit will usually slip off to one side. Even if it doesn't you 
are still left with enough of the thing left in the threads to have difficulty getting it off.

Secondly, PB-Blaster takes some time to penetrate, IFF it is going to.

Thirdly, since the knobs are usually aluminum, they form an aluminum oxide around the 
set-screw which is extremely hard to penetrate by penetrating oil. Others are brass, and 
brass is "sticky".

Alternate heat from a BIG soldering iron or torch (but below the melting point of aluminum) 
and cold, like putting the entire unit in the freezer for an hour or two, then application of as 
much torque via your Bristol wrench as you safely can, will eventually break that sort of 
set-screw free.

Keep working on it: you'll get it.

Ken W7EKB