I tried a new (to me) tool yesterday—a step drill bit:
The purpose of a step drill is to drill large holes in thin material (like sheet metal) neatly. Yesterday, I needed to drill ½” holes in a plastic project box for the USB-to-DMX adapter that my son and I are working on (him much more than me). Because the holes had to be very precisely placed, I decided to try using the step drills I’d bought earlier this summer, though I could have also used a ½” Forstner bit for such a soft material.
To use the step drill, I first drilled a starter hole (3/32″) smaller than the smallest size on the bit (1/8″), then I changed bits on the drill press and carefully aligned the bit to be centered on the starter hole. Because I was going all the way to the largest size on this drill bit, I did not have to set the stop on the drill press—if I’d wanted a ⅜” hole, I would have needed to make sure not to drill too deep. Because I was drilling plastic, I did not need oil for cooling and lubricating the bit, as I would have if I were drilling sheet metal. Drilling the hole was very fast, and the hole was quite clean.
It may not have been necessary to drill the starter hole, but the tip of the step drill did not look that sharp to me, so I figured that the extra step of making a starter hole was worth the time. Some of the bigger starter bits really do need a starter hole to enlarge.
I have several step drill bits now, because I bought two sets from Harbor Freight when they had a coupon sale on them earlier this summer:
The bits are cheap and probably not likely to last long drilling hard materials (like stainless steel), but I’ll mainly use them for plastic and aluminum, and I don’t need to drill very many holes with them to justify the price.