I am using some old riding lawnmower axle shafts in my new welding cart.
I inserted them in the ends of .065 wall, 1 inch square tubing.
I drilled and tapped a hole to 1/4 x 20 thread, for a set screw.
I need to make a depression, or hole for the set screw to fit into.

My drill dosen't seem to make a dent in it, will my end mill do it?
What other methods are available?