My suggestion. Mark them for drilling, threading, cutting, and take them to a machine shop.
I had read in previous posts that the door hinges can be a pain. But, that is an understatement.
After dulling multiple 5/16" high speed drills, two tough steel countersinks (on two holes, eight needed), and breaking a tap in a partially tapped hole, I gave up and found a friendly machine shop.
For about $50, I could have escaped all the mental anguish, costly bits and countersinks, and cutting off the 1/4 steel to length.
I let the "Built, not bought" slogan slip a bit on this task.
And, I haven't even gotten to the fitting and adjustment yet.

Just thought I'd share.

Ralph