Best Overall
Bosch CO14 Cobalt Set
- Pieces
- 14
- Material
- M42 Cobalt Steel
- Shank Type
- 3-Flat
- Size Range
- 1/16 in. to 1/2 in.
Pros
- Bites into stainless steel, cast aluminum, and mild steel without walking or chattering.
- Build quality and sizing consistency outclass many similarly-priced cobalt sets.
- Edge retention stays sharp after repeated holes, reducing replacement frequency.
Cons
- Cobalt's extreme hardness makes bits brittle; flexing, dropping, or off-angle hand drilling can snap smaller diameters.
M42-grade cobalt steel and a split-point tip allow these bits to start on contact in hardened stainless, cast iron, and alloy steel without a center punch. The 3-flat shank locks securely into the chuck, preventing slip on larger sizes. Cutting edges hold up through repeated holes in material that dull standard TiN bits within seconds. Slow speeds and cutting oil produce clean, burr-free results.
This set targets metalworkers and fabricators who drill stainless steel regularly and are comfortable with the discipline of low RPMs, cutting oil, and a drill press or very stable hand. It's not for wood-only shops or those unwilling to adapt technique — lateral force or a drop can snap smaller bits. For that tradeoff, you get a durable, imperial-sizes kit in a well-organized case.
💡 Tip: Always use cutting oil and a drill press when possible; cobalt's heat resistance works best at low RPMs to avoid brittle failure.
Bottom line: If stainless steel is a regular drilling target and you can give it a drill press or rock-steady hand with cutting oil, the CO14 delivers professional-grade results that TiN sets cannot match.
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