Best Drill Bits for Metal: HSS, Cobalt or Carbide?

For most metal projects, start with a quality high-speed-steel bit for aluminum and mild steel, or a cobalt-alloy bit for stainless steel and harder alloys. A 135-degree split point helps reduce walking. Sheet metal usually calls for a step bit, while solid carbide belongs mainly in rigid machining setups. The “best” drill bit depends on the work material, hole diameter, machine rigidity and whether you can control speed and feed.

This guide recommends bit types, not a universal brand winner. Even an excellent bit will rub, overheat or break if it is run too fast, fed too lightly, allowed to wobble or used in an unclamped workpiece.

Best drill bit for each metal

HSS, cobalt, coated HSS or carbide?

High-speed steel (HSS)

HSS is the economical general-purpose choice for softer nonferrous metals and ordinary mild steel. Sharp geometry and correct technique matter more than a decorative finish. HSS is also less brittle than carbide, making it forgiving in a handheld drill, although any bit can break if side-loaded.

Cobalt-alloy HSS

Cobalt is alloyed through the steel rather than painted onto the surface. That helps the cutting edge retain hardness at elevated temperatures and allows the bit to be resharpened without removing the benefit. Bosch’s official M42 cobalt-bit information lists stainless steel, cast iron and other demanding metal applications. Cobalt bits are harder but less tolerant of flex, so keep the drill aligned.

Titanium and black-oxide coatings

A coating can reduce friction, improve corrosion resistance or increase surface wear resistance, depending on the coating. It does not turn a weak substrate into a cobalt bit. Sharpening a coated cutting edge removes coating at that edge, so evaluate the underlying steel as well as the package color.

Carbide

Carbide offers high wear and heat resistance but is brittle and sensitive to vibration and runout. Solid-carbide drills make sense in rigid drill presses, mills and production machinery with controlled feeds. A handheld drill is rarely the right environment for expensive solid-carbide tooling.

Point geometry and bit design

• 118-degree point: a common general-purpose geometry for softer materials and ordinary work.
• 135-degree split point: designed to start with less walking and often used for harder metals. DeWalt’s official cobalt split-point specification describes a 135-degree tip for accurate starts.
• Step bit: efficient for enlarging holes in sheet metal within the bit maker’s thickness range.
• Short/stub-length twist bit: extra rigidity can reduce wandering and breakage when reach is not needed.
• Annular cutter: useful for larger holes with the correct magnetic drill or machine; it is not a twist-bit substitute for every setup.

How to drill metal without burning the bit

1. Identify the metal. Mild steel, stainless, aluminum and hardened fasteners do not behave the same.
2. Mark and support the hole. Use an appropriate punch or starting method, then clamp the work securely.
3. Select speed from authoritative guidance. Larger bits and harder materials generally require lower spindle speeds, but use the drill-bit or machine maker’s chart rather than one universal RPM.
4. Keep a sharp edge cutting. A squealing bit that produces dust instead of chips may be rubbing. Stop, inspect the edge and correct speed/feed before adding force.
5. Use the right cutting fluid. Follow the tool and material manufacturer’s advice; fluids differ by alloy and operation.
6. Clear chips safely. Stop the machine before reaching near the bit or removing swarf. Never use bare hands on sharp chips.

Metal-drilling safety

Wear appropriate eye protection and follow the machine manual. Clamp the work rather than holding it by hand. OSHA’s drill-press safety guidance identifies rotating tooling, hot chips and hand-held stock as hazards and recommends work-holding fixtures. Do not wear gloves, loose clothing or jewelry around rotating drill-press components; secure long hair. Disconnect power before changing belts or servicing equipment.

What to look for in a metal drill-bit set

• the bit material stated clearly—not just a color;
• sizes you actually use, including replacements for common small diameters;
• a split-point option for accurate starts;
• a case that protects cutting edges and labels each diameter;
• manufacturer application and speed guidance;
• availability of individual replacement bits.

For hard or heat-resistant steel specifically, continue to our drill bits for hardened steel guide. For a broader material overview, see drill bits for wood, metal and masonry.