You're standing at the tool crib or scrolling an industrial supplier and there are three price tiers staring at you: standard HSS, cobalt, and carbide. The prices range from reasonable to "are you serious." The question is whether the premium is justified for what you're actually doing.
What it is: The standard. HSS (M2 grade is most common) is a tungsten-molybdenum steel alloy that holds a sharp edge at elevated cutting temperatures. It's been the shop floor standard for decades.
Best for:
Heat tolerance: Good up to about 600°C. Past that the edge softens and you start losing geometry fast.
Resharpenable? Yes. This is the primary advantage of HSS. A properly resharpened HSS bit performs exactly like a new one. The economics are clear: resharpening a 1/2" HSS bit costs a fraction of replacement, and the bit returns to full performance.
Cost: Lowest of the three. A quality M2 bit in 1/2" runs $5–15 depending on brand and source.
Bottom line: If you're drilling mild steel, aluminum, brass, or plastics — HSS is the correct choice. Don't pay for cobalt or carbide you don't need.
What it is: HSS with 5–8% cobalt added to the alloy. The cobalt increases heat resistance and hardness at temperature. M35 (5% cobalt) is more common. M42 (8% cobalt) is used in more demanding applications.
Best for:
Heat tolerance: Good up to about 900°C — roughly 50% better than standard HSS. This matters when you're drilling stainless, which generates heat fast and work-hardens if you let the bit dwell.
Resharpenable? Yes. Cobalt bits resharpen on the same equipment as HSS. Especially on larger diameters where a new cobalt bit is $30–50, resharpening makes clear economic sense.
Cost: 2–4x HSS. A 1/2" M35 cobalt bit runs $15–40.
Bottom line: If you're drilling stainless or hard alloys, cobalt pays for itself quickly by outlasting multiple HSS bits. For mild steel or aluminum — don't bother.
What it is: Tungsten carbide, either as a solid rod ground into a drill or as carbide inserts brazed onto an HSS body. Solid carbide drills are common in CNC production.
Best for:
Cutting speed: Significantly higher than HSS or cobalt — carbide can run 3–5x the surface footage of HSS in the right application. In CNC production with coolant-through tooling, the throughput difference is substantial.
Carbide is brittle. Interrupted cuts, hard inclusions, or chatter can chip or fracture carbide where HSS would just dull. Setup rigidity matters far more with carbide than with HSS.
Cost: 5–20x HSS. Solid carbide 1/2" drills run $40–150+.
Bottom line: Carbide makes sense for CNC production runs, hardened materials, and composites. For job shop and general machining — HSS or cobalt with proper speeds and feeds will outperform the wrong carbide grade in the wrong application every time.
| Material | Recommended | Notes |
|---|---|---|
| Mild steel | HSS | Standard 118° works well |
| Aluminum | HSS | Higher rake, lighter cut fluid |
| Stainless 304/316 | Cobalt | HSS dulls fast — cobalt earns its cost |
| Hardened steel | Cobalt or Carbide | Depends on hardness level |
| Cast iron | HSS or Carbide | Dry, no cutting fluid |
| CNC production | Carbide | Speed and volume justify cost |
| Plastics | HSS | High speed, light feed, peck drill |
When you send drills for resharpening, tell us what materials you're running. We grind geometry to match the application — not just back to a generic 118°.
Get a resharpening quote →