Quick answer: the best drill bit for metal is a cobalt twist bit (M35 or M42) with a 135° split point. It cuts mild steel, stainless and cast iron, and it keeps its edge when it gets hot. For mild steel and aluminum on a budget, titanium-coated HSS is enough. For thin sheet metal, a step bit beats any twist bit.
So the right bit depends on two things: the metal and its thickness. Use the chart below, then see the picks, a speed chart and the most common questions.
Best Drill Bit by Metal and Thickness
| Metal | Thin (under 1/8 in. / 3 mm) | Medium (1/8 to 1/4 in. / 3–6 mm) | Thick (over 1/4 in. / 6 mm) |
|---|---|---|---|
| Mild steel | Step bit or titanium HSS | Titanium HSS or cobalt | Cobalt with a pilot hole; annular cutter for big holes |
| Stainless steel | Cobalt, or a step bit at low speed | Cobalt (M35 or M42) | M42 cobalt, low RPM, cutting oil |
| Hardened or alloy steel | M42 cobalt | M42 cobalt | M42 cobalt or carbide; drill press |
| Aluminum, copper, brass | Step bit or HSS | HSS or titanium HSS | HSS twist bit; carbide hole saw for big holes |
| Cast iron | Cobalt | Cobalt | Cobalt, run dry or with light oil |
In our shop, the M42 cobalt drill bit covers the hard cases: stainless, alloy steel and thick plate. If you mostly drill mild steel and aluminum, the 13-piece titanium HSS drill bit set is the low-cost starting kit. For sheet metal, junction boxes and panels, a nitride-coated step drill bit drills clean holes from 4 to 32 mm without a pilot hole.
How to Choose a Drill Bit for Metal
1. Match the bit material to the metal
| Bit material | Good for | Skip it for |
|---|---|---|
| Black oxide HSS | Mild steel, aluminum, copper, occasional use | Stainless, hardened steel |
| Titanium (TiN) coated HSS | Mild steel and aluminum, longer life than plain HSS | Heavy stainless work (the coating wears off the tip) |
| Cobalt M35 (about 5% cobalt) | Stainless, cast iron, alloy steel, everyday steel work | Concrete |
| Cobalt M42 (about 8% cobalt) | Thick or hard steel, many holes in stainless | Side loads (more brittle) |
| Carbide-tipped (hole saws) | Large holes in steel and stainless sheet | Wobbly setups |
The key difference: TiN and black oxide are surface treatments. Cobalt is alloyed through the whole bit, so it stays hard when hot and still cuts after you resharpen it. To see the M42 and M35 bits next to our step bits and carbide hole saws, browse our cobalt drill bits for stainless steel and other metals.
2. Match the bit type to the hole
- Up to 1/2 in. (13 mm): twist bit. Cobalt for stainless and hard steel.
- Thin sheet, several sizes: step bit. One bit, clean round holes, little burr.
- About 3/4 in. to several inches: hole saw. Carbide-tipped for steel and stainless.
- Large holes in thick plate: annular cutter on a mag drill or drill press.
3. Look for a 135° split point
A standard 118° point has a wide chisel edge at the center that skates on smooth metal. A 135° split point starts on center, needs less push, and wanders less. If a bit keeps walking off your mark, this is the spec that fixes it.
4. Pick a shank that fits your drill
Round shanks fit any 3-jaw chuck. Hex and three-flat shanks can't spin under torque. Annular cutters need a matching holder on a mag drill.
The 7 Best Drill Bits for Metal in Our Shop
1. M42 Cobalt Drill Bit: Best Overall for Steel and Stainless
M42 Cobalt Drill Bit (8% Cobalt HSS) · from $8.99 per bit; 13-piece set $48.99
- M42 high-speed steel with 8% cobalt for hardness and heat resistance.
- 135° split point that starts on center without walking.
- Fully ground spiral flutes that clear chips fast.
- Metric single bits from 3.0 to 13 mm, or a 13-piece set from 1.5 to 6.5 mm.
- Listed for stainless (including 304), steel plate, cast iron, aluminum, copper and wood.
Who it's for: anyone who drills stainless, thick steel, or a lot of holes. Honest limit: sizes are metric, and M42 is harder but more brittle than M35, so keep the drill straight and avoid prying.
2. M35 Cobalt Jobber Bit: Best for Replacing Single Sizes
Cobalt Drill Bit, M35 HSS Jobber · from $7.99 per bit
- M35 high-speed steel with 5% cobalt.
- Sold individually from 0.5 to 13 mm, so you only replace the sizes you wear out.
- Straight round shank for standard 3-jaw chucks; polished flutes.
- Listed for stainless, cast iron, alloy steel, aluminum and wood.
Who it's for: metalworkers who burn through the same two or three sizes. Honest limit: no set option, and the listing doesn't specify a split point, so center-punch your mark first.
3. Titanium HSS Drill Bit Set: Best Budget Set for Mild Steel
13-Piece Titanium HSS Twist Drill Bit Set · $17.99
- 13 metric HSS twist bits with a titanium coating that reduces friction and edge wear.
- Supplier-listed hardness of about HRC68.
- Anti-adhesion coating helps keep material from building up on the edge.
- Listed for steel, stainless steel and other metals; also cuts wood and plastic.
Who it's for: DIYers who need a full set of sizes for brackets, repairs and pilot holes before tapping. Honest limit: titanium is a coating, not an alloy. Once the tip wears or you resharpen it, it cuts like plain HSS. For daily stainless work, step up to cobalt.
4. Nitride-Coated Step Drill Bit: Best for Sheet Metal
Nitride Coated HSS Step Drill Bit · from $9.99 per bit; 3-piece set from $47.99
- HSS with a nitride coating to reduce friction and run cooler.
- 4–12 mm (5 steps), 4–20 mm (9 steps) or 4–32 mm (15 steps, 2 mm increments).
- No pilot hole needed, and the next step deburrs the hole as you drill.
- Listed for thin steel and iron plate, aluminum, insulation panels, PVC sheet and wood.
Who it's for: electricians, HVAC, auto and anyone drilling panels and boxes. Honest limit: made for thin plate, not thick steel, and sizes can vary 1–3 mm from the stated measurement. Water or oil cooling extends bit life.
5. Steel Hole Saw With Tungsten Carbide Tip: Best for Big Holes in a Hand Drill
Steel Hole Saw With Tungsten Carbide Tip · from $21.99 (35 mm) to $99.99 (120 mm)
- YG10X tungsten carbide teeth on a 45# carbon steel body.
- 20 mm working depth.
- Listed for stainless up to 4 mm thick, plus aluminum, iron, angle iron and cast iron.
- Works in a hand drill or drill press.
Who it's for: plumbers, electricians, and fabricators cutting conduit and fixture holes. Honest limit: one size per saw, and the listing calls for a tight pilot bit, a square start, and cutting fluid on thicker metal.
6. HSS Annular Cutter: Best for Thick Plate
HSS Annular Cutter, 6 to 60 mm · from $34.99
- Cuts only a ring and leaves a solid slug, so it needs less power and makes less heat than a twist bit of the same size.
- Diameters from 6 to 60 mm with 35 mm cut depth; some sizes also in 55 mm depth.
- Listed for steel plate, stainless, cast iron, angle iron, aluminum, copper and brass.
Who it's for: fabricators and steel erectors with a mag drill. Honest limit: it needs a mag drill or drill press, not a handheld drill. Sold as a single cutter, and the listing allows 1 to 3 mm variance in stated dimensions.
7. Drill Bit Sharpener Attachment: Best Add-On
Drill Bit Sharpener Attachment · $16.99
- Runs on your drill with a standard hex shank.
- 3 slots for bits from 2.0 to 12.5 mm (5/64 to 1/2 in.).
- Corundum grinding wheel plus a spare wheel.
Who it's for: anyone with a drawer of dull twist bits. A sharp edge matters more on metal than almost anything else. Honest limit: it's a quick field sharpener, not a precision grinder, so it won't create a split point.
Comparison Table
| Product | Best for | Size range | Price | Needs |
|---|---|---|---|---|
| M42 Cobalt Drill Bit | Stainless, thick or hard steel | 3–13 mm; 13-pc set 1.5–6.5 mm | From $8.99 | Any drill, low speed |
| M35 Cobalt Jobber Bit | Replacing single sizes | 0.5–13 mm | From $7.99 | Any drill |
| Titanium HSS Set (13 pc) | Mild steel, aluminum, budget | 13 metric sizes | $17.99 | Any drill |
| Nitride Step Drill Bit | Sheet metal, boxes, panels | 4–12, 4–20, 4–32 mm | From $9.99 | Thin material |
| Carbide-Tip Hole Saw | Large holes, stainless to 4 mm | 35–120 mm | From $21.99 | Pilot bit, cutting fluid |
| HSS Annular Cutter | Thick plate | 6–60 mm | From $34.99 | Mag drill or drill press |
| Drill Bit Sharpener | Restoring dull bits | 2.0–12.5 mm | $16.99 | Your drill |
Drill Speed for Metal: RPM Chart
Metal needs lower speed than wood, and stainless needs the lowest. These are common starting points for HSS and cobalt bits, using RPM = (surface feet per minute × 3.82) ÷ bit diameter in inches.
| Bit size | Mild steel (80–100 SFM) | Stainless (30–50 SFM) |
|---|---|---|
| 1/8 in. (3 mm) | 2,400–3,000 | 900–1,500 |
| 1/4 in. (6 mm) | 1,200–1,500 | 450–750 |
| 3/8 in. (10 mm) | 800–1,000 | 300–500 |
| 1/2 in. (13 mm) | 600–750 | 230–380 |
Aluminum and brass can run faster than mild steel. If you see smoke, blue chips, or hear squealing, slow down and push harder.
5 Tips for Drilling Metal
- Clamp the work. Thin metal that spins or flexes ruins bits and fingers.
- Center-punch the mark. It gives the tip a seat so it can't walk.
- Pilot holes over 1/4 in. A small pilot cuts the force you need for the big bit.
- Use cutting oil on steel. It keeps the edge cool and helps chips clear.
- Keep it cutting. Steady pressure should make curled chips. Fine dust means the bit is rubbing.
Related Guides
- Best Drill Bits for Stainless Steel: full method and RPM chart for the hardest common metal
- Types of Drill Bits: all 14 bit types and what each one is for
- Why Does My Drill Bit Keep Slipping?: fixes for bits that walk on metal or spin in the chuck
FAQ
What is the best drill bit for metal?
A cobalt (M35 or M42) twist bit with a 135° split point covers most steel, including stainless. Use a step bit for thin sheet and a carbide-tipped hole saw for holes over about 3/4 in.
What is the best drill bit for thick metal?
For holes up to 1/2 in. in thick steel, an M42 cobalt bit at low speed with cutting oil, after a smaller pilot hole. For larger holes in plate over 1/4 in., an annular cutter on a mag drill or drill press cuts faster and runs cooler.
What is the best step drill bit for metal?
An HSS step bit with a coating (nitride, titanium or cobalt) and steps in the sizes you use most. Step bits are for sheet metal and thin plate. They are not made for thick steel.
Is cobalt or titanium better for drilling metal?
Cobalt for stainless and hard steel, because the cobalt runs through the whole bit and keeps its edge when hot. Titanium-coated HSS is fine for mild steel and aluminum, but the coating wears off the tip.
What are the different types of drill bits for metal?
Twist bits (black oxide, titanium, or cobalt), step bits for sheet metal, hole saws for large holes, and annular cutters for thick plate on a mag drill.
Can I use a wood drill bit on metal?
No. Brad point, spade, and auger bits are shaped for wood fibers and dull or break on metal. Use an HSS or cobalt twist bit.
Why does my drill bit stop cutting metal?
Usually the bit is dull or spinning too fast. On stainless, rubbing also hardens the metal. Slow down, add oil, push harder, and sharpen or replace the bit.