[Boatanchors] SI units and the rest

[jmfranke]

The grid ring on a 416B triode is threaded 3/4"-40.

John  WA4WDL

--------------------------------------------------
From: "Kludge" <wh7hg.hi at gmail.com>
Sent: Wednesday, November 17, 2010 1:07 PM
To: <boatanchors at mailman.qth.net>
Subject: Re: [Boatanchors] SI units and the rest

> 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!
>
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