Milwaukee 48-89-2370 RED HELIX Cobalt Drill Bit Set (15-Piece) Review (2026)
By The DIYPicks Team · Updated July 2026
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- Metal
- Stainless steel
- Hard metals
The Milwaukee 48-89-2370 is a 15-piece M35 cobalt drill bit set (1/16 to 3/8 in) engineered for stainless, hardened steel and cast iron. Because cobalt is hard all the way through, it keeps cutting where coated HSS overheats, and Milwaukee's Quad Edge tip plus a variable RED HELIX flute start faster and clear chips to fight the heat that kills metal bits. It costs more than titanium sets but earns it on tough metal, though round shanks can slip under heavy torque.
Pros
- Solid cobalt runs cool and lasts up to 15x longer than black-oxide bits in hard metal
- Quad Edge tip has four cutting edges for faster starts and less walking
- Variable 35-to-15-degree RED HELIX flute ejects chips quickly to reduce heat
Cons
- Costs more than titanium-coated HSS sets
- Round shanks can slip in keyless chucks under high torque
- Overkill for wood and plastic where cheaper bits do the job
Specifications
| Material | Cobalt (M35) |
|---|---|
| Sizes | 1/16 - 3/8 in (15 bits) |
| Shank | Round straight |
| Point | 135 deg split point (Quad Edge) |
| Best for | Stainless, hardened steel, cast iron, angle iron |