Metallics NHSDC21 High-Speed Twist Drill Bit 21" 3-1/4" Blk Ox (1pc)

The Metallics NHSDC21 is a high-speed twist drill bit stated at 21 inches and 3-1/4 inches. The 21 inch figure is the length that lets it reach through studs, joists and plates from a single access point, which is why electricians reach for a bit this long rather than a standard jobber bit.

One bit per pouch. The NHSDC21 is a single-piece item supplied in a pouch, so if you want spares on the truck you order multiple units rather than getting several in a box.

A 21 inch high-speed twist bit like the NHSDC21 is the tool for reaching across or through multiple framing members from one position, typical of rough-in wiring work. An auger or self-feed bit pulls itself through wood faster at larger diameters, but it needs to start square on the face of the member. Where you are drilling at an angle, through a plate from inside a bay, or through mixed material, the twist geometry tracks better and is less likely to grab.

The NHSDC21 is a black oxide finished high-speed steel bit. Black oxide adds surface lubricity and corrosion resistance over bright HSS, which helps on long boring runs through wood framing where chip clearance and heat build-up are the limiting factors.