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Cobalt bits · stainless

Bosch Professional HSS-Cobalt ProBox, 19 pieces

Cobalt bits, which exist for one reason: stainless steel work-hardens and ordinary HSS gives up.

Bosch Professional HSS-Cobalt ProBox, 19 pieces, product photograph

Bosch Professional HSS-Cobalt ProBox, 19 pieces

Cobalt bits, which exist for one reason: stainless steel work-hardens and ordinary HSS gives up.

Material
HSS-Cobalt (HSS-Co)
Quantity
19 bits
Named use
Stainless steel
Amazon reference
B009CGDSYI
EAN
3165140689786
  • Cobalt alloy holds its edge at the temperature stainless generates
  • A 19-piece set covers the common sizes in one box
  • More brittle than plain HSS — they chip if the work moves

Best for: Anyone who has burnt out ordinary bits trying to drill stainless

≈ $66
Check price on Amazon

Specifications

Material
HSS-Cobalt (HSS-Co)
Quantity
19 bits
Named use
Stainless steel
Amazon reference
B009CGDSYI
EAN
3165140689786

The technique matters as much as the bit

Low speed, firm continuous pressure, and cutting fluid. A cobalt bit used at 2,000 rpm with light pressure will still glaze stainless — the alloy buys margin, not immunity.

One set, many jobs

Nineteen sizes covers the everyday range. Larger holes in steel belong to step drills or annular cutters rather than to twist bits, which struggle above about 13 mm (0.51 in) on a bench machine.

Sources

Every figure above comes from the manufacturer’s published specification for this reference. Fields the listing does not publish are left out rather than estimated. Market availability was verified per market on the EAN.

The questions welders ask

Why does stainless destroy ordinary bits?

Because it work-hardens. Rubbing rather than cutting — which is what happens when a bit is dull, the speed is too high or the feed too light — turns the surface layer glass-hard, and from then on nothing will cut it. Cobalt bits keep their edge hotter, so they keep cutting instead of rubbing, which is how they avoid the trap.

Are cobalt bits better for everything?

No. They are harder and therefore more brittle, so in a hand drill with a workpiece that can move they chip where an HSS bit would flex and survive. For mild steel, sharp HSS at the right speed with cutting fluid is cheaper and just as effective.

Welders this fits

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