Metallics NHSD43 High-Speed Twist Drill 43 2-1/4" (10pcs)

The NHSD43 is a wire gauge No. 43 bit, which cuts a 0.089 inch hole. That is the standard pilot size for tapping a 4-40 machine screw thread, which is why electricians keep it on the truck for drilling and tapping junction box ears, enclosure covers, and small device mounting holes. Overall length is 2-1/4 inches.

A No. 43 bit, which is what the Metallics NHSD43 is, is the standard pilot for a 4-40 tap. Drill with the No. 43, then run the 4-40 tap in. If you want a looser clearance hole instead of a tapped thread, you need a larger gauge, not this one.

Ten bits per pack, supplied in a pouch rather than loose or on a carded blister. Since a No. 43 bit is small enough to snap when it binds in sheet steel, the ten pack is sized for a crew that goes through them.

High-speed steel handles the material an electrician actually drills on site: sheet steel boxes and enclosures, aluminum, brass, plastic, and wood. Step up to cobalt or carbide only when you are going into stainless or hardened plate. For a 0.089 inch No. 43 bit, keep the speed up and the feed light, because a bit that small walks and snaps easily in thin steel.

Order Metallics MPN NHSD43. The Metallics NHSD numbering runs by wire gauge size, so the 43 in the number is the drill size and adjacent gauges carry their own numbers. Confirm the gauge, not just the series, when you order.