Even if you’re not building an airplane, you probably have need to bore holes in metal from time to time. In this continuing series by our sister publication KITPLANES, Paul Dye explains the finer points of using a step drill, sometimes also called a UnitBit. Basically, it makes a big hole out of a smaller hole and is especially handy when you don’t have very large drill bits for metal. (Few of us do.)

Paul Dye
Paul Dye, KITPLANES® Editor at Large, retired as a Lead Flight Director for NASA’s Human Space Flight program, with 40 years of aerospace experience on everything from Cubs to the Space Shuttle. An avid homebuilder, he began flying and working on airplanes as a teen, and has experience with a wide range of construction techniques and materials. He flies an RV-8 that he built, an RV-3 that he built with his pilot wife, as well as a Dream Tundra they completed. Currently, they are building a Xenos motorglider. A commercially licensed pilot, he has logged over 5000 hours in many different types of aircraft and is an A&P, EAA Tech Counselor and Flight Advisor, as well as a former member of the Homebuilder’s Council. He consults and collaborates in aerospace operations and flight-testing projects across the country.


  1. Those things are great. They also work well using them in a drill press. I couldn’t have finished my plane without a selection of those things.