Use a hydraulic press to gradually and smoothly increase pressure until the broach is forced through.
Making a sqaure hole sheet metal.
Making a square hole in a plough blade.
How to make a square hole without using special tools.
At first locate the center of the whole.
Now it s time to use that center punch.
Put your ink to the use and mark the hole center.
Go slow and drill a smaller hole first ti guide the bigger rill bit.
If the hole is a lot bigger then your biggest drill bit then drilling holes round the edge of the square and then connecting them with a saw is the best way for you.
Blacksmithing for beginners cutting a square hole in sheet metal.
How to use chisels instead of files to cut a share hole for carriage bolts.
Drill a hole in the metal close to but smaller than the finished hole size.
Ensure you fix the metal sheet down when you drill do not hold in you hand.
This will create dimples in the sheet.