[Hammarlund] SP-600 Knob and tag removal help!

[Barry Hauser]

Cecil Acuff writes:
>         Anyone have any experience at removing a set screw that has 
> had it's internal hex shoulders stripped.  It is frozen and finally 
> stripped.  I had tried penetrating oils before applying too much 
> pressure, but to no avail.  I am trying to save the knob...it is one 
> of the main tuning knobs.  
<snipped> 
> Anyone have any better ideas that you may have used....

Here are some techniques I've used in the past, generally in combination:
 

*Apply a very small amount of epoxy to the end of the allen wrench,
carefully insert without getting any in the wrong places, allow to set
fully before trying again.  It might be better to use a wire to put some
in the allen screw socket instead.

*Take a larger allen key -- might have to be a metric of the next largest
size and work it in or tap it in with a small hammer to cut its way into
the allen socket. 

* A variant of the above:  Sacrifice the next largest allen key -- test
fit and file each of the six sides down until you get a snug fit.  May
also need to tap it in to get it to grab.

* Put the receiver on end, hold onto the flywheel to keep it from moving
and try twisting the knob, if not completely off, then just to break the
tip of the allen screw loose from the shaft, then try a larger key.

* Apply heat to the setscrew by heating the end of the allen key with a
high wattage soldering gun.  Then allow to cool. This probably won't do
you much good now that the socket has been stripped.

* Someone recently suggested first tightening a stuck screw before
attempting to remove it, as a way to break it free.  I've never tried
this.

Best bet is a combination of the above such as:  First try breaking the
knob free if you can by putting the radio on end, keeping the shaft from
turning from the back of the panel and twisting the knob. The idea is to
get the tip of the screw free from the shaft a bit. It would be good if
you could manage a barely a few degrees of rotation back and forth.  Then
file or grind the next larger size allen key to fit the setscrew tightly.
 Keep the sides flat and edges sharp as you grind and keep test fitting
it as you go.  If it isn't perfectly symmetrical, don't worry about it. 
When it seems like it might grab well enough, tap it into place.  Then
take a shot at backing it out.  It's not easy and it usually takes a few
cut 'n tries.

> Also....has anyone tried to remove the rather thick aluminum tag 
> that is glued to the front center of the panel on the VLF version.  
> If you have not seen one it is about 2" X 2.5" and probably 1/8 th 
> inch thick...it looks like it was applied much like the metal 
> property tags that many companies put on their equipment.  
> 
> I can't imagine trying to strip the front panel with aircraft 
> stripper without damaging the paint on the tag.  Any prying would 
> only destroy the tag for sure.  I thought about maybe heating the 
> panel from the rear ever so carefully in hopes of softening the glue 
> that holds it in place.  Reattaching it should not be a problem if I 
> can just get the thing off to allow me to refinished the panel.

I've used that spray-on aircraft stripper.  Never removed a glued on tag,
although I've had them fall off ;-).  I would suggest very carefully
masking the tag, overlapping the masking onto the panel with at least 1/2
inch of overlap.  You can sand rather than strip that last 1/2 inch in
advance of stripping, which will minimize the chance of the stripper
undermining the masking through the paint.  However, pre-test the masking
with the stripper on some scrap metal to make sure it doesn't eat through
or soak through the stuff.  Masking tape is probably the worst choice.  I
would think layers of vinyl or electrical tape, maybe duct tape would be
safe.  Then, after all the paint is stripped, you generally have to sand
anyway.  Use a good grade of wet/dry or perhaps just Scotch-Brite.  Don't
use steel wool at all.  Fragments break off and dig into the pits in the
metal and invariably show up in the finish. When ready to prime and
paint, then remove the old masking and replace with regular masking tape,
precision trimmed with a razor or Xacto knife.  When masking, you might
want to put some paper or foil over the main part of the tag if there is
any chance that the adhesive will lift the paint or otherwise mess it up,
particularly if using duct tape. (or "duck tape"  quack quack)

If you really want to remove the tag, which I don't recomend unless the
glue is failing at least on one corner, you might get it started with a
single edge razor blade, preferably in a holder, like one of those
scrapers.  You'll only be able to get it started.  Then you would need a
very thin strip of metal to tap through under the tag.  One of those thin
flexible stainless steel rulers comes to mind, or some shim stock, but I
think the ruler is the best bet.  Then tap with a hammer flush with the
panel.  You don't want to bend that tag.  This may result in some
scarring of the panel which you'll be covering over anyway.  I haven't
ever quite done this in the same situation, but similar maneuvers.

Hope some or any of this helps. 

Barry

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