[Hallicrafters] Knarly Knurl Nuts - Was: Removing Toggle Switches

[Chris Kepus]

For diversion from the normal Sat night stuff, the availability of a knurl
nut wrench got my attention.  Just last week I fought and lost a battle to a
knarly knurl nut which tenaciously held tight to a toggle switch I wanted to
remove.  (of course I tried the reverse side trick!).  I hate to mar a front
panel, no matter what the panel is fronting!!

So, tonight, after seeing this toggle switch knurl nut thread, I headed for
the GC site.  As reported earlier, there are two knurl nut wrenches listed
on GC electronics; a 1/2" and a 5/8"; About $27 and $30 respectively. 

Then, I Googled for knurl wrenches.  Sure enough, another site listed the GC
1/2" wrench for $23 and change.

OK, this is good, let's keep going.  A hit further down the search list was
from the Antique Radios forum.  A 2007 thread on the same subject also
explored options to marring the front panels or tearing up the knurl nut
(there *really* isn't a question that's not been asked before, is there?).
On this particular thread, one gent pointed to this site,
http://www.tessco.com/products/displayProductInfo.do?sku=477526&eventPage=1.
Tessco,  two years later, still carries the GC 1/2" wrench for.... (Drum
Roll!).... $15.75!

But........what size does one buy?  

Well, I grabbed my faithful analog micrometer and went out to the shack and
started measuring:

On my S-76, are 4 knurl nuts hanging onto toggle switches:  They measured:
0.574, 0.566, 0.569, 0.569.  Hmmmm. All a bit larger than a 9/16" OD.
(0.5625)

On my SX-100, there are also 4 knurl nuts. They measured: 0.569; 0.597
(what?!), 0.592 (what, again?!), 0.569.  This is getting complicated.  Will
one knurl nut wrench accommodate a range of knurl nut OD's from 0.569 to
0.597?

On my GPR-90, there are 5 knurl nuts, They measured: 0.598, 0.598, 0.599,
0.615, and 0.610.  Now I'm really confused! Maybe the OD's are bigger
because TMC spent more money on knurl nuts. (the toggle switch threaded
diameter was essentially the same on all I measured)

So I went to the junque box, pulled out a standard (? - well, it looked
"standard") toggle switch, went to the hardware drawer, managed to find 5
knurl nuts; then proceeded to make sure all five knurl nuts threaded onto
the same toggle switch.  After I had five out of five winners (which, BTW,
the OD's varied enough such that the nikked human eyeball could detect that
the OD's were not the same), I proceeded to measure the OD of these knurl
nuts.  They measured: 0.564, 0.557, 0.598, 0.563, 0.573. 
 
For additional contrast and comparison, I found three hex nuts that fit the
same toggle switch treads.  They all measured 0.562 +/- .001. 
A standard 9/16" socket or open end wrench fits these hex nuts. 

Back to the knurl nuts:  The opening (ID) on several 9/16 sockets and
wrenches I measured is 0.567 (+/- .001).  If the knurl nut wrench ID is,
say, 0.568; it would not have been able to handle two of the knurl nuts on
the S-76 and two of the knurl nuts on the SX-100. (Unless it expands to
0.600)  

Conclusion:  Get the specs on the range of knurl nut sizes the GC knurl nut
wrench accommodates before throwing money at it....or hopefully someone who
owns a couple will clue us in. 

73 
Chris
W7JPG


 

__________ Information from ESET Smart Security, version of virus signature
database 3948 (20090319) __________

The message was checked by ESET Smart Security.

http://www.eset.com