[Collins] 75A4...Name the type set screws holding dial drum to shaft

[Dr. Gerald N. Johnson]

www.americanradiosupply.com/bristol-ss-408-bristol-spline-wrench-set-for-collins-75a-4-receiver/
  shows 9 sizes of splines were used in the 75A-4. They sell a set. Its
probably less expensive to buy the individual bristol spline wrenches or
a set from McMaster-Carr (www.mcmaster.com).

Otherwise if it can be found the Xcelite 99PS-60 Spline
Screw-driver Set can be handier than L wrenches.
www.qth.net/pipermail/boatanchors/2009-May/023173.html
I've owned that set for at least 40, maybe closer to 50 years.

I haven't been into a 75A-4 so I can't say what sizes were used. And
nobody but you can detect if the set screws have been replace or are
original. I'm sure the originals were bristol splines. Its totally
practical to have replaced any or all of them with hex or slotted set
screws if any needed to be replaced after being lost in the carpet or
damaged by using the wrong tool to extract them.

I didn't find mention of the briston wrenches in two editions of the
75A-4 manuals I have in this computer.

Many set screws were locked with paint or lacquer well before the days
of loctite anaerobic thread locker.

If a smaller hex wrench goes in than the spline that goes in, that is
sign that the set screw is spline, not hex.

73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association

On 6/25/2014 1:06 PM, John King via Collins wrote:
> I need to remove the dial drum from my 75A4 and can't tell whether
> the set screws holding the drum on the shaft are Bristol spline set
> screws or Allen head screws? I don't want to strip out the screws
> ruin them. I cannot see well enough to determine the correct tool to
> loosen the two set screws holding the dial drum to the shaft. I am in
> the process of replacing the dial drum overlay.
>
> If someone knows for sure whether Bristol or Allen tool is the
> correct on for this application, PLEASE share that information to me.
> I am well aware that folks sometimes ruing Collins knobs by failing
> to use the correct tool for the job. Thanks and 73, John, K5PGW
> ______________________________________________________________
>