How drill bits are made

Cut the steel rod

Most modern twist drills use high-speed steel, a high-carbon tool steel that keeps its hardness up to a red heat of around 650 °C. Bar or rod is cut into lengths close to the finished tool.

around 650 °C red hardness

Grind the outside diameter

The cut rod's outside is ground to the specified sizes for the barrel and the shank, before any of the cutting geometry exists.

Harden the rod

Heat treatment makes the rod harder. Blasting with particles or a chemical wash then strips off the thin film of deposits it leaves behind.

Grind the flutes

A flute grinding machine cuts one groove, the rod turns half a circle in its chuck, and the machine cuts the second. These grooves carry chips out of the hole.

Or forge and twist

Rolled bits replace the flute grinding with forging. The steel is heated, flattened and twisted to shape, a much shorter process. They come out cheaper, but often more brittle and less accurate.

Shape the point

A contoured wheel forms the flank surfaces at the tip. Rolled bits often get a 118° tip, while ground bits for hard metal get a flatter 135°, sometimes split so they start without a pilot hole.

Coat the surface

Some high-speed steel bits get a titanium nitride coating, which adds strength and lowers friction when drilling hard materials.