At first locate the center of the whole.
Making a sqaure hole sheet metal.
Use your center punch to strike at the center of the hole.
How to use chisels instead of files to cut a share hole for carriage bolts.
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.
Now it s time to use that center punch.
Insert the broach and ensure it lines up at 90 degrees from the work peice or the hole will be crooked.
Drill a hole in the metal close to but smaller than the finished hole size.
Next use a compass to outline the edge of the hole.
Put your ink to the use and mark the hole center.
Blacksmithing for beginners cutting a square hole in sheet metal.
Use a hydraulic press to gradually and smoothly increase pressure until the broach is forced through.
Go slow and drill a smaller hole first ti guide the bigger rill bit.
How to make a square hole without using special tools.