[Boatanchors] SI units and the rest

[Kludge]

From: WA5CAB at cs.com [mailto:WA5CAB at cs.com] 
> The other basic design flaw in metric threaded fasteners (to be reusable
after a few years in 
> the normal dirty world) is that screw and bolt heads and nuts are smaller
relative to 
> diameter.  As are screw slots.  So that the amount of torque that you can
put on a partially 
> rusted fastener before the wrench rounds off the corners and turns without
turning the 
> fastener is much lower.  

Yep.  Heat, WD-40 and other tricks don’t always help.  [BA content] These
screws are found in the rice boxes so popular for so long, including the
hollow state ones from "back then."  They don't always loosed well even in
that "pristine" application.  I think sometimes they're made that way so the
screws & nuts do get destroyed thus guaranteeing further sales.  :-)

> And actually, in this regard, the Whitworth (the oldest) thread standard
is better than either 
> USS or SAE as the hex sizes are slightly larger on both BW and BSF. 
Whoever designed it 
> (I assume someone named Whitworth) obviously put some thought into the
overall design of 
> the system.  Which obviously didn't happen with any of the several metric
systems that you 
> run into today.

Let's see ... what Western countries have the longest traditions in
mechanical engineering.  Oh, yeah - Scotland, England and the US.  (Think:
Industrial Revolution.)  The Whitworth standard is English as are several
others, all based on the inch just like USS, SAE and UN* threads.

> There are also several thread pitches where the pitch is the same across
multiple diameters.  
> -16 being perhaps most common in the smaller sizes.  

-40 is another which I know goes to 1/4" and may go larger.  A lot of the
UNEF threads I've encountered are used in gun making. 

> I must have run into one of these in a boatanchor sometime in the past as
well, as I have a 
> 3/4-16 UN tap in my tap cabinet.

That thread is used on some smaller lathe headstocks for mounting chucks.  I
think some tooling adapters for larger machines do as well.  (You and I work
at totally different scales so ... :-) )

Although it only has 3 tubes and a bunch of fused sand thingies, the
RT-671/PRC-47 still kind of counts as a boatanchor even if by weight alone.
Anyway, the antenna thread is 3/8-16 where the normal antenna thread is
3/8-24.  After my current project is in hand and I get the lathes set up,
one thing I plan is to make some adapters from some 1" hex brass stock on
hand, not only for that but also to accept a PL-259 (which adapter I know
already exists) since I'll have the stock handy.  At least one of the thread
adapters will be made so the radio can be operated horizontally with a whip
attached rather than standing on its back.  There may be others but that's
the general game plan.

Best regards,
 
Michael, WH7HG BL01xh
http://www.nationalmssociety.org/chapters/NTH/index.aspx 
http://wh7hg.blogspot.com/ 
http://kludges-other-blog.blogspot.com 
Hiki Nô!