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Re: [TowerTalk] [RFI] Back of desk grounding buss

To: Bryan Swadener <bswadener@yahoo.com>, towertalk@contesting.com
Subject: Re: [TowerTalk] [RFI] Back of desk grounding buss
From: Charlie Gallo <Charlie@TheGallos.com>
Reply-to: Charlie Gallo <Charlie@TheGallos.com>
Date: Thu, 20 Mar 2014 23:53:20 -0400
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
On 3/20/2014 Bryan Swadener wrote:

> I make connection to it using machine screws and _TEE NUTS_.
> Where I want a connection, I drill a hole to accept a Tee
> nut, and press it into the back using a C-clamp. Then, the
> connection can be made using only a capscrew, as tight as
> you like.

One thing I don't worry about is how to make a connection that won't pull out.  
I have a machine shop, and know the tricks.  It all depends, there are 
different ways to do it.  Like I said, more than three threads (NC) and you 
usually won't have a problem.  That said, the hole has to be on size, properly 
tapped etc (for material that CAN be roll tapped, roll taps are the way to go). 
 Assuming we are talking Cu (or AL), and 1/4-20 studs, 1/8 doesn't GIVE you 3 
threads, you need to go at least 3/16, and for Cu, you probably want to go 1/4" 
(hard to get 7/32 stock).  

If it is thinner than that, you can bolt through (as some have said), or 
better, press in some headed studs from the back side (something like a type 
TFE pem stud) 
http://www.fastenal.com/web/products/details/0127639?searchMode=productSearch&zipcode=&filterByStore=&filterByVendingMachine=

(you can also get copper studs)



I know how to make connections to Cu (or Al - the internal tooth star washer 
works well), the question was more "OK, we know Cu (well, silver, but) is the 
best, but is Al OK".  There has been some arguments among local hams if the 
difference in conductivity would make any difference (I was on the NO side) but 
some were "The difference on conductivity will increase the voltage rise enough 
to cause issues with a lightning strike" 


-- 
Charlie

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