You are talking the drills with 1/2 inch straight shanks , correct? We have a post drill at the Boy Scout camp smithy, I made a few different size drills from 1/2 inch 0-1 drill rod. Turn down ( or grind or forge ) down to the desired drill size and make into a simple spade drill. Harden , temper and go ... these flute-less spade drills work good, chip extraction is not an issue since most holes are not deep.
Joe B