[Hallicrafters] knob retaining screws

[Roy Morgan]

At 12:37 PM 10/4/2007, you wrote:
>... set/grub screws holding knobs on
>that are not allen or slotted screw, they seem to be 4
>sided. What type are they

Douglas,

They are four-slot BRISTOL spline set screws.  I am working on an SX-88 
which uses:

the six-flute .096 inch spline screws in:
  - the band switch shaft couplings
  - the band switch knob

and four-flute smaller diameter spline set screws in most other places 
(Including the gearbox, which I have completely dis-assembled.)

>and where is a good place to
>find a wrench to remove them?

The place to get *genuine* Bristol Wrench Company USA produced, highest 
quality tools is at Max Gain Systems.  I recently got long L-wrenches in 
three sizes for about $2 each.   If you call now, they would be in the mail 
to you tomorrow, or maybe today:

Max-Gain Systems:
http://www.mgs4u.com/Bristol-spline-L-keys.htm
221 Greencrest Ct., Marietta, GA 30068-3825
Phone: (770) 973-6251
Fax: (815) 461-7730
Email: <mailto:info at mgs4u.com>info at mgs4u.com

These folks have straight wrenches chucked in screwdriver handles, one for 
each size, short arm and long arm individual wrenches, and kits.  Their 
SS-508 kit is likely to do all you need, and is priced at $14 plus $2 sh.

They have a special to get a very nice allen wrench kit in addition for a 
modest amount more. "Special combination price! The HS-206 if purchased 
WITH the SS-508 Bristol spline L-key kit are priced at $18.95 plus $3 
shipping in US and possessions, $4 worldwide. Ask for the "HS-206 combo". "

There are two sizes of 4-flute set screws you may have run into:
S-069-4, or S-076-4
The three digits in the middle are the size in thousandths of the outer 
diameter of the wrench:  I suspect it is the S-076-4 that you need.  If you 
intend to order only the minimum to get you covered, discover the size of 
an allen wrench that seems like it should fit.  (Note that allen wrenches 
are sized from flat to flat, not max outer diameter.)

R-390 receivers use the 6-flute .096 size.
HP instruments with very small knobs use the smaller or smallest 4-flute size.

I have three suggestions:

1) Do not order from Snap-On. You'll pay as much for one wrench as you do 
for all you need from Max-Gain.  Do not go down to Sears or any other place 
looking for these - they don't have them.
2) order from Max-Gain and get the best available
3) break the sharpness of the end of the wrench with a very fine sharpening 
stone to make it easier to get it into the set screw


The Xcelite 99-series wrench inserts with handles (Tee and screwdriver 
type) are very good also.  They make a kit with handle, extension, and nine 
wrench inserts.  Mouser lists these inserts as individual parts but most of 
them are described as "discontinued".  The Xcelite tools are not 
discontinued by Xcelite, or their distributor which is:

Cooper Tools apparently supplies Xcelite sets to retailers:
Cooper Tools, Inc (Xcelite):
http://www.cooperhandtools.com/brands/xcelite/index.cfm

Another source is:
Newman Tools, Inc.:
http://www.newmantools.com/hand/splinekey.htm

Call Max-Gain now.

Roy


- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing
13033 Downey Mill Road, Lovettsville, VA 20180
Phone 540-822-5911   Cell 301-928-7794
Work: Voice: 301-975-3254,  Fax: 301-975-6097
roy.morgan at nist.gov --