[R-390] R390 knob set screw

[Barry Hauser]

Hi John

Coincidentally, I have a question about JB Weld.  I just used it to repair a 
small folding table which was inadequately glued to start with.

I'm more accustomed to regular and quick-cure epoxy which is clear.

Had some small tube sets of JB weld somewhere, but lost track of it.  I 
picked up some at Pep
Boys -- big box "J-B Industro Weld, Cold Weld Shop Size"

This stuff when mixed is medium to light gray.  Are all of the J-B Welds 
that color?  I also picked up the small tubes of the quick set version.

That grey looks very similar in shade to the "right" shade for R-390 front 
panels.  Anyone try it to detail out a chip?  Might not even need touch-up.

I used to assume J-B was the same basically as regular epoxy glue, but 
possibly better quality.  Must be something very different as it doesn't 
have that characteristic annoying aroma.  It also cleans up a heck of a lot 
easier.

Barry

----- Original Message ----- 
From: "John KA1XC" <tetrode at comcast.net>
To: "R-390 reflector" <r-390 at mailman.qth.net>
Sent: Thursday, April 14, 2005 12:21 PM
Subject: Re: [R-390] R390 knob set screw


> Dan,
> my notes say it's 8-36 UNF thread, yet another oddity of the 39x's. If you
> had the tap you could epoxy the hole and drill and retap it but a
> replacement knob can be gotten cheaper.
>
> Sometimes you can smear some JB Weld across just the damaged area, let it
> firm up a bit, and then use the setscrew itself as a tap, then remove it 
> and
> let the JB cure. If your lucky it can give the setscrew the little extra
> bite it needs to do the job.
>
> That phenolic insulating shaft on the 390 is pretty tough, I wouldn't 
> worry
> too much about hurting it.
>
> John
>
>
> ----- Original Message ----- 
> From: "Dan Merz" <djmerz at 3-cities.com>
> To: <r-390 at mailman.qth.net>
> Sent: Thursday, April 14, 2005 12:22 AM
> Subject: [R-390] R390 knob set screw
>
>
>> Hi,  I ran into a minor problem.  The set screw in one of the larger 
>> knobs
>> (on the ant trim on R390) doesn't want to tighten against the shaft and I
>> see that the threads in the knob are damaged in the area near the shaft
> and
>> the screw likes to just ratchet back at the critical point of tightening.
>> It's the knob not the set screw that's the problem.  I think a longer set
>> screw of 3/8 length would solve the problem.  What is the thread
> size/pitch
>> on these set screws? I make it to be 8-36, an unusual size these days.
> Are
>> there some screws longer than the standard 1/4 inch length in somebody's
>> pile?  The other alternative is to drill and tap it for the next larger
> size
>> set screw but who wants one knob to have a different size wrench, hi?  I
>> guess I could shove a piece of solder or piece of plastic in front of the
>> short one and hope for the best.  The trimmer shaft looks like phenolic 
>> so
>> I'd like to treat it nicely.  Any advice on fix appreciated,  more later,
>> Dan.
>>
>>
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