Milwaukee Black and Bronze Drill Bit Set Review

Drill bit marketing runs on finishes, and most of them are doing less than the packaging implies. It is worth being precise about this one.

Black and bronze oxide is a surface treatment applied to high-speed steel. It does not make the bit harder. What it does is reduce friction between the flute and the chip, which slows heat build-up. Heat is what destroys drill bits in metal — the edge anneals, loses temper and stops cutting, usually in the last third of a hole when the chips are struggling to clear. Less friction means a cooler bit, which means more holes per bit.

So the finish is worth having for metal work, and worth nothing in timber, where heat is not the failure mode.

The set is 14 jobber-length bits in the common fractional sizes, which is enough coverage that you are not constantly hunting a single size.

Where they run out

In stainless, hardened steel, or anything you would describe as “tough”, the base material matters more than the coating. Cobalt bits (M35 or M42) have the alloy through the whole bit rather than a treatment on the outside, and they hold an edge at temperatures that will ruin these. If half your drilling is stainless, buy cobalt and accept the price.

And for woodworkers

A twist bit is the wrong tool for a clean hole in timber. The point wanders on start, and the exit tears out because there are no spurs to sever the fibres first. Brad-point bits have a centre spur and cutting spurs on the rim and produce a hole with clean walls and a clean exit.

Own both. This set for metal and rough work, a brad point set for anything that shows.

One technique note

These have a standard 118-degree point rather than a split point, which means the chisel edge at the centre scrapes rather than cuts and the bit will skate on a smooth surface. Centre-punch first. It takes two seconds and removes the single most common cause of a hole in the wrong place.