Blacksmith Drill Bits

Blacksmith drill bits are large-diameter high speed steel drills with a reduced shank, made to drill big holes in metal using an ordinary drill. This guide explains the reduced shank and when to use one.

Why the reduced shank matters — On a normal bit the shank is the same width as the cutting end, so a large-diameter bit would need an equally large chuck. A blacksmith bit is turned down to a smaller, standard shank, so a wide cutting diameter fits a standard 13mm chuck. That means you can drill large holes with the drill or pillar drill you already own, without stepping up to a bigger machine.

What they suit — These are for opening large-diameter holes in steel, plate and general metal, either drilling straight to size or enlarging a smaller pilot hole. The ground flute clears swarf over the larger cut.

How to drill large holes cleanly — Drill a pilot hole first to guide the bit, run at a slow speed suited to the diameter, and use a cutting lubricant with firm, steady pressure. Large bits cut best slow, so let the bit work rather than forcing the speed.

Choosing a size — Match the diameter to the hole you need, and check the shank fits your chuck. Order the individual sizes you use most, or a set to cover a range.

For standard-diameter drills see our HSS Drill Bits collection, and for the toughest materials see HSS Cobalt.

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