Klein Tools 25964 13-Step Drill Bit, Double-Fluted, 1/8-Inch to 1/2-Inch

The 25964 steps from 1/8 inch up to 1/2 inch (3.2 to 12.7 mm) in 13 separate hole sizes, climbing in 1/32 inch (0.8 mm) increments. That increment is the thing to check against your job: at 1/32 inch steps you get a size close to almost any small conduit fitting, grommet, or cable gland you are drilling for, rather than jumping a full 1/16 like a coarser bit. Each step is laser etched with its size so you can count where you are mid cut.

Either one. The 25964 has a 1/4 inch hex shank and an impact rated shaft, so it chucks straight into a standard 1/4 inch hex impact driver as well as a keyless drill chuck. For a panel or enclosure job that means you can stay on the impact driver you already have on your belt instead of carrying a second tool up the ladder.

Steel up to 16 gauge is the rated limit for this bit, and it also cuts wood, plastic, and aluminum. That covers most sheet metal enclosures, junction boxes, device boxes, and light gauge duct. Heavier structural steel or plate is past what a step bit like this is meant for, so for anything thicker than 16 gauge use a hole saw or a knockout punch instead.

No pilot hole needed. The 25964 has a split point tip that bites and starts the cut on its own without skating across the panel, which is the usual reason a plain twist bit needs a center punch first. Start it square, let the first step establish the hole, then feed steadily through the steps until you reach the etched size you want.

Two spiral flutes rather than one. The 25964 carries dual spiral fluting, which clears chips from both sides of the cut and helps pull the bit through the material, so it cuts faster and loads up less on sheet steel. A single flute design is simpler and cheaper but tends to need more feed pressure and more chip clearing on a run of holes. If you are drilling one or two openings a single flute is fine; if you are punching out a whole enclosure or a run of boxes, the double flute earns its place.

Compact. The bit measures 3.43 inches (8.7 cm) on its long axis and 0.5 inch across, and weighs 0.06 lbs. Add the length of your impact driver and that is your total reach into the box. In a shallow panel or a wall cavity where a hole saw and arbor would not swing, this profile usually will.

The TiN coating on the 25964 dissipates heat, which is what kills step bits, they overheat at the cutting edge and lose temper. The bit body itself is high speed steel, and the coating is what lets it shed the heat built up drilling repeated holes in steel. On a job where you are drilling dozens of openings back to back it is the difference between one bit lasting the job and going dull halfway.