Being the cheap *** that I am. I took an old deep socket 11/16" and took it over to the bench grinder where I quickly ground two flat spots on the sides of the socket, one on each side. Then I use a crescent wrench to mount the socket and it works like a charm. The Allen wrench fits right up the center of the socket.

 

I have an O-Ratchet socket set that works great.

http://www.ebay.com/sch/i.html?_nkw=...het+socket+set

 

I have an 11/16 socket with flats on it for a wrench, allen wrench goes thru the middle....works great.

 

1/2-20 I believe.

 

I think its a hardened nut, not just one out of a bin. If you dont have an 11/16" sub a 17 mm.

 

A grade 8 but will be fine.