The density of angle iron requires special techniques to drill a hole through the steel while keeping the drill bit sharp. Friction between the cutting tip of the drill bit and the surface of the angle iron creates heat at the drilling point. This heat increases the rate the drill bit dulls as you drill. As the drill bit dulls, heat builds at a faster rate. Controlling heat build-up keeps the drill bit sharper longer and allows you to drill through the angle iron at a faster rate.
Pull a tape measure along a length of angle iron. Mark the length location of the hole with an awl. Pull the tape measure across the width of the angle. Mark the centre of the angle with the awl. The two marks must cross to show the centre of the hole you will drill through the angle.
Hit the back of a centre punch with a hammer while the tip of the punch sits aligned with the intersection of the two awl marks. Pour cutting fluid on the depression made by the centre punch.
Secure a 1/8-inch drill bit into the chuck of a variable speed drill motor. Set the tip of the installed drill bit on the enter punch depression. Pump the trigger of the drill to slowly drill through the angle iron. Keep the speed of the drill motor slow to avoid overheating the drill bit.
Remove the 1/8-inch drill bit from the drill motor.
Install a step drill bit into the chuck of the drill motor. Coat the drill bit and the 1/8-inch hole in the angle iron with cutting fluid. Set the end of the step drill bit into the 1/8-inch hole. Slowly drill the hole until the correct step of the drill bit cuts through the angle iron.
Mark the step of a step drill bit with a paint for easier identification while drilling through angle iron.
Wear safty glasses to keep metal debris from entering your eyes.