Guys- I recall reading quite a long time ago that for efficient industrial forging a hammer should have 50 # of ram weight for every 1 square inch of cross section. Does anyone else recall this recommendation and where it came from? If I had to guess I'd say old Chambersburg literature but it could have been in an old book. 

yes that is the correct rule of thumb if you scour you will find it but that is general info if your doing steady industrial work

 

I found the source finally. It comes from some Chambursburg literature on their self contained hammers. There is a table which shows that a 5000 lb hammer can work 10 inch square alloy steel on a production basis.