[TowerTalk] [RFI] Back of desk grounding buss

[Charlie Gallo]

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