Metallics HSSC16E Drill Bit HD Cobalt St 135d SplPt 5/16" 4-1/2" YLW (1pc)

Cobalt is the reason to pick this one. The HSSC16E is a heavy duty cobalt bit, so it holds its edge at the higher temperatures you get cutting stainless, cast iron, and tougher alloys, where a plain high speed steel bit dulls or work-hardens the hole. It also drills mild steel, aluminum, and strut channel without issue.

It's a straight round shank, so it goes into any 3/8 inch or larger keyed or keyless drill chuck. It will not lock into a 1/4 inch hex quick-change impact driver holder, so if your crew runs impact drivers only, you need a hex shank bit instead.

A 135 degree split point starts cutting on contact, so you can drill sheet metal, enclosure walls, or strut without center punching first and the bit is much less likely to walk across the surface. The flatter 135 degree angle also spreads the cutting load, which is what you want in hard material. A standard 118 degree point needs a punch mark to stay put.

One bit per pouch. The HSSC16E is sold as a single piece in a pouch, not as an index or assortment, so if you are stocking a van or a shop crib you order the quantity of 5/16 bits you want rather than getting a size range.

Yes, that's the application it's built for. A cobalt 135 degree split point bit is the electrical trade standard for drilling through strut channel, junction box and panel walls, and steel studs, because it self-starts on a vertical surface overhead and survives galvanized steel. Metallics catalogues the HSSC16E in its electrical supply line.