Best Drill Bits for Metal: Step Bits vs. HSS vs. Cobalt
Best Drill Bits for Metal: Step Bits vs. HSS vs. Cobalt
Drilling through metal is harder on tooling than wood or plastic, and using the wrong bit wastes time and money. Here's a breakdown of the three most common drill bit types for metal work — step bits, HSS, and cobalt — and when to use each.
HSS (High Speed Steel) Drill Bits
HSS drill bits are the standard general-purpose metal drilling bit. They can withstand the heat generated by drilling without losing hardness, making them suitable for most common metals.
- Best for: Mild steel, aluminum, copper, brass, and most non-ferrous metals
- Not ideal for: Stainless steel, hardened steel
- Coating options: Black oxide (basic), TiN (harder, longer life), TiAlN (best for high-heat)
- Cost: Lowest of the three
Bottom line: HSS bits are the right choice for everyday metal drilling. Keep a full set on hand for general use.
Cobalt Drill Bits
Cobalt bits are HSS with 5–8% cobalt added. The cobalt increases heat resistance and hardness, making these bits significantly more durable when drilling hard or abrasive materials.
- Best for: Stainless steel, hardened steel, cast iron, titanium
- Key advantage: Can be resharpened multiple times
- Cost: Higher than HSS, lower than carbide
Bottom line: If you're regularly drilling stainless or hardened materials, cobalt bits pay for themselves quickly.
Step Drill Bits
Step bits are cone-shaped with multiple stepped diameters on a single bit. One bit drills a range of hole sizes without changing bits.
- Best for: Sheet metal, electrical panels, thin-gauge steel, aluminum, plastic
- Key advantage: One bit drills multiple sizes; self-centering; clean holes with minimal burr
- Common size ranges: 1/8"–1/2", 3/16"–3/4", and larger
Bottom line: Essential for any shop doing electrical work, trailer wiring, or sheet metal fabrication.
Head-to-Head Comparison
| Feature | HSS | Cobalt | Step Bit |
|---|---|---|---|
| Best material | Mild steel, aluminum | Stainless, hard steel | Sheet metal, thin stock |
| Heat resistance | Good | Excellent | Good |
| Hole size flexibility | One size per bit | One size per bit | Multiple sizes per bit |
| Resharpenable | Yes (limited) | Yes | No |
| Cost | Low | Medium | Medium |
Tips for Drilling Metal Successfully
- Use cutting fluid — reduces heat and extends bit life significantly.
- Start slow, finish fast — lower RPM to start, increase once engaged.
- Use a center punch — prevents the bit from walking across the surface.
- Let the bit do the work — steady moderate pressure; excessive force generates heat and breaks bits.
- Clear chips frequently — back the bit out periodically to clear chips.
Shop Drill Bits at Chem Nut Supply
Chem Nut Supply carries HSS drill bit sets, cobalt drill bit sets, and step drill bit sets in complete shop kits. Shop our Drill Bits & Cutting Products collection for the full selection.