It's a spring loaded die set for 3/8" round stock.  Not certian what it's called. Top, and bottom tools in one, fits the hardy hole, and sits on the anvil.  I figure when I get close, I can use it to get dimension exact.   Still needs some work, (I didn't drill the hole deep enough, so I need to use my die grinder to finish)  And I'm afraid the spring is a bit stiff, but time will tell.

   Please overlook my welding. I was going for penetration, and holding, not purdy. :) 

It's called a spring swage and it looks like it will work just fine.

Nice job.  So now that it's been in operation for a while, what changes have you made to it or was it "good to go" after you cleaned up the hole?  Thanks for sharing.

  

I left the edges too sharp, so a little chamfering and it works fine.