Drill Bits for Metal | Choose the Right Bit Every Time

One wrong bit choice turns a five-minute job into a ruined workpiece and a smoking drill. The difference between a clean hole and a wandering, overheated mess comes down to three variables: the bit’s material, its point angle, and the speed you run it at. Here is what actually works for the metals you drill most.

The Four Bit Types That Cut Metal

Every metal drill bit falls into one of four material categories, and picking the wrong one is the most expensive mistake beginners make. Here is what each one handles best.

High-Speed Steel (HSS)

HSS bits work fine for mild steel, aluminum, copper, and thin sheet metal. They lose their edge fast above 600°F, so they are not the choice for hardened steel or stainless. For light fabrication and hobby work, a good HSS set from Irwin or Bosch delivers solid results at a low price.

M35 Cobalt (5% Cobalt)

Cobalt steel stays hard at higher temperatures than plain HSS. M35 contains 5% cobalt and handles standard carbon steel, cast iron, and occasional stainless work. It is the best price-to-performance middle ground for a general shop.

M42 Cobalt (8% Cobalt)

M42 is heavier on cobalt, giving it exceptional red-hardness — the ability to stay sharp at cutting temperatures exceeding 1,100°F. These bits slice through hardened steel, stainless 304 and 316, and tough alloys without softening.

Solid Carbide

Solid carbide is brittle but unmatched in hardness. Use these only for extreme-hard alloys, armor plate, or production work where speed matters more than impact resistance. Brands like Cle Line, Norseman, and Drill USA earn the premium price here.

135° vs. 118° Point Angle — What Changes

The point angle determines whether the bit bites into metal or skates across it. A 135° split point is standard for hard metal: it starts cutting immediately without a center punch and virtually eliminates wandering on hardened steel and stainless. A 118° point works better for softer metals like aluminum and copper, where a flatter tip can grab too aggressively.

On tough steel, always reach for a 135° bit with a split-point grind. The four-facet grind on premium cobalt bits starts cutting the instant it touches the metal, and that saves you the frustration of re-centering a drifted hole.

Matching the Bit to the Metal — The Table

The Right Speed for Each Size

Speed kills bits faster than anything else when working with metal. Big diameters generate heat far faster than small ones, so RPM must drop as bit size climbs.

For a 1/2-inch bit in stainless steel, run a drill press at 200–400 RPM. For a 1.5-inch bit in mild steel, stay at 100–150 RPM — higher speeds glaze the edge instantly. Small bits under 1/8 inch can run at 1,500–2,500 RPM, but that rule reverses fast once you cross 3/8 inch. When in doubt, choose the lower speed; a slow, steady cut outlasts a rushed one every time.

Drilling Technique That Keeps Bits Sharp

Technique matters more than any coating or brand name. The steps are simple but skipping one ruins the result.

• Press firmly. Hard enough that chips exit constantly without stopping. Light pressure lets the bit rub and overheat.
• Keep the drill moving. A stationary bit welds itself to stainless within seconds. Steady feed prevents chip welding.
• Use cutting oil. For stainless steel especially, oil is not optional — it extends bit life by double or more.
• Drill slowly. Rushing generates friction heat that softens the bit’s edge. Let the bit do the work at its own pace.

For holes larger than 1.5 inches, switch to a TCT tungsten carbide tipped annular cutter. Twist drills this size generate too much heat and torque — annular cutters remove a ring of material instead and cut faster with less strain on drill and user.

Coatings — Black Oxide vs. Titanium

Black oxide adds moderate heat resistance and lubricity for iron and steel. It is economical and works well for general fabrication, but it is not suitable for aluminum or magnesium — the coating reacts poorly with those metals.

Titanium nitride (TiN) is more expensive but adds real surface hardness and a thermal barrier. TiN-coated bits handle steel, aluminum, and magnesium with less friction and longer edge life. For anyone drilling a mix of materials in an impact driver, TiN makes sense. For a dedicated metal shop running mostly steel, black oxide or plain cobalt is enough.

Best Drill Bits for Metal: A Quick Verdict Table

For a deeper look at what works on the toughest materials, our tested roundup of bits for hardened steel covers the exact models that survive the hardest jobs.

Common Mistakes That Ruin a Metal Drilling Job

Most failed metal holes come from three predictable errors. Knowing them ahead of time saves bits and scrap.

• Using the wrong bit type. Masonry bits (welded carbide points) cannot cut metal — they are designed to hammer brick. Wood bits with spade points go blunt instantly in steel. Only use bits labeled for metal.
• Running large bits at drill-press speeds. A 1-inch twist drill at 1,000 RPM overheats so fast the edge discolors within seconds. Drop RPM as diameter climbs.
• Skipping the center punch on 118° bits. Standard 118° bits skate on hard metal unless you center-punch first. A 135° split point eliminates the need — switch to split-point bits for hard metals and skip the punch step.

Safety When Drilling Metal

Kickback is the real danger with larger holes. A bit that catches the edge of a hole can spin the workpiece or wrench the drill out of your hands. Use a drill press for holes over 1/2 inch, or a drill with a long handle that gives you leverage. Secure the workpiece with clamps — never hold it by hand on a press.

Quality control matters: a bit that cuts poorly is often dull from the factory or made from low-grade steel. If a bit from a known brand underperforms, sharpen it by hand on a bench grinder — if the steel is good, it will come back. If it keeps failing, discard it.