hot riveting bumper support plates into a diamond t 980 

morning Lee yes they are 1/2" dia shank rivets and the jam back has a 4" dia piston, it is all over kill but we always work with 5/8" to 7/8" dia shank rivets so all the riveting gear we have is set up for that.

Thanks for the reply. I am involved in the restoration of a railcar where we need to install around 100 1/2 inch rivets. We have got access to a suitable rivet gun but not a backing up tool. I have seen some videos where they have backed up with a large/heavy bar. Do you think this would give reasonable result for a half inch rivet?

if you have the room you can oppose gun that works very well i don't think holding a heavy bar behind the rivet will work to well but depends on the size of your rivet gun in relation to the size and weight of the bar. some of the other riveting i have done on the diamond t chassis i couldn't use a jam back so i made a tool which is basically a T shape but hinges were the 2 pieces meet. so it works a bit like a over centre chain binder if that makes sense so as you pull on the lever it gets tighter that works perfectly even on 3/4" rivets.