What Type of Drill Bit Is Best for Drilling Steel

For ordinary mild steel, use a high-speed steel (HSS) twist bit with a 135-degree split point; for stainless steel, thicker stock, and tougher steels, a cobalt-alloy twist bit is usually the better choice. The bit must be sharp and intended for metal, but drilling technique matters just as much: excessive speed and heat can ruin even a good bit. Choose the bit for the steel type and hole size, then drill at low speed with steady pressure and cutting fluid.

What Makes a Drill Bit Work in Steel

Steel is harder and less forgiving than wood, plastic, or aluminum. A suitable bit needs a hard cutting edge, flutes that carry metal chips out of the hole, and a point shape that starts without skating across the surface.

HSS is the standard material for general-purpose metal drilling. Despite the name, high-speed steel is a type of hardened tool steel, not an ordinary hardware-store “steel bit.” It can drill mild steel, steel pipe, flat bar, and many common repair materials when it is sharp and used correctly.

Cobalt-alloy bits are a better upgrade for stainless steel and other harder metals because they tolerate heat better than ordinary HSS. They are not simply coated bits: cobalt is part of the drill-bit alloy. That matters when the hole takes long enough to generate substantial heat.

Do not choose solely by color. Gold-colored titanium-nitride-coated bits can be useful for lighter metal work, but a coating does not turn a general-purpose bit into a durable stainless-steel bit.

How To Drill Steel Successfully

Use this guide to select the bit before marking and drilling the workpiece.

Steel job	Best starting bit choice	Why it fits
Mild steel, steel pipe, flat bar, and common brackets	HSS twist bit with a 135-degree split point	Starts cleanly and cuts ordinary steel effectively
Stainless steel or other difficult hard metals	Cobalt-alloy twist bit	Better heat resistance and durability
Thin sheet steel with a larger finished hole	HSS step bit	Enlarges holes progressively with less grabbing
Large hole in thin or moderate-gauge steel	Metal-rated bi-metal hole saw	Removes a circular plug rather than drilling out the whole diameter
Hardened steel	Carbide bit specifically made for hardened steel	Ordinary HSS and cobalt may only rub or skate
Ordinary steel beam or thick structural steel	Cobalt-alloy twist bit, or an annular cutter in appropriate equipment	Cobalt handles the demanding cut better than basic HSS

Step 1: Identify the Steel and Select the Bit

Treat a clearly identified mild-steel bracket, tube, or bar as an HSS job unless the hole is large, deep, or numerous.
Choose cobalt for stainless steel, thick stock, repeated holes, or a job where a ruined bit would be costly or inconvenient.
For ordinary steel, look for an HSS bit whose product specification lists a 135-degree split point.
Check the exact bit, not only the product family name. DEWALT Cobalt Alloy Steel Drill Bits may have a PILOT POINT, split-point, or chisel-point tip, depending on the SKU. Each is intended to start on contact and reduce walking, but not every cobalt bit uses the same tip shape.

Step 2: Secure the Workpiece and Prepare the Location

Wear safety glasses and clear loose clothing, jewelry, and hair away from the drill.
Clamp the steel firmly to a drill-press table, workbench, or other stable support. Never hold a small steel piece in one hand while drilling with the other.
Mark the hole center with a marker.
Make a small dimple at that mark with a center punch and hammer. The dimple gives the bit a place to start and prevents it from wandering over the smooth steel surface.

For a larger finished hole, start with a smaller pilot hole only when the bit or hole saw calls for one. A pilot hole can make it easier to keep a large bit centered, but it is not a substitute for clamping and center-punching.

Step 3: Lubricate the Cut and Drill at Low Speed

Apply cutting fluid or cutting oil to the drill point and marked area.
Set the drill to its low-speed range rather than running the trigger at maximum speed.
Hold the drill square to the steel and begin with firm, controlled pressure.
Keep enough pressure on the tool for it to make small metal chips. If it only squeals, polishes the surface, or produces dust-like debris, stop before the bit overheats.
Add more cutting fluid as the hole deepens. Withdraw the bit occasionally to clear chips from the flutes, then resume drilling.

Drill steel slowly rather than fast. Larger-diameter bits and harder steels need lower speed because their cutting edges travel farther around the hole and create more heat.

Step 4: Ease Through the Breakthrough

Reduce pressure as the bit approaches the far side of the steel. This helps prevent the bit from grabbing as it breaks through.
Let the bit fully exit the hole, then release the trigger and wait for the tool to stop.
Remove the clamp only after the workpiece and bit are no longer moving.
Deburr both sides of the hole with a countersink, deburring tool, file, or sandpaper. A drilled hole can look clean while still having a sharp metal edge.

A clean result is a centered hole with no sharp burrs, no blue heat discoloration around the opening, and no rough spiral marks caused by a dull or wandering bit.

When a Cobalt Bit Is Worth the Extra Cost

Stainless steel, repeated holes, deep holes, thick stock, and larger drill diameters are especially likely to make heat the limiting factor because they create more friction than a single small hole in mild steel.

For stainless work, DEWALT’s Cobalt Alloy Steel Drill Bits are specified by DEWALT to deliver 4 times longer life in stainless steel. That is a product-line claim for that stainless-steel application, not a promise that every cobalt bit will last four times as long in every type of steel.

Product tests can also be useful when the material and conditions closely match your project. In a drill-press comparison using 10 mm holes in 6 mm-thick SUS304 stainless steel at a constant 400 rpm, the Adiseal Ultimate metal drill bit drilled 135 holes and averaged 31.7 seconds per hole. The best Bosch cobalt bit in that same test drilled 15 holes and averaged 132.4 seconds per hole, while a non-cobalt Bosch PointTeQ bit did not complete a hole in that stainless-steel stock.

Those results apply to that particular test setup, bit size, and grade of stainless steel. They do show why a hard-metal-rated bit is a meaningful purchase decision for substantial stainless work, rather than assuming every bit labeled for “metal” will perform the same way.

Choosing Bits for Special Steel Jobs

Sharp HSS, cobalt, carbide, step bits, and annular cutters suit different steel jobs, from thin sheet to hardened steel and structural members.

Thin Sheet Steel

Thin sheet is prone to grabbing and tearing as a standard twist bit breaks through. For a small hole, use a sharp HSS or cobalt twist bit and reduce pressure near the exit.

For a larger hole, a step bit often produces a rounder, cleaner opening because it expands the hole in stages. Support the sheet from beneath, clamp it securely, and stop at the step matching the desired hole size.

Stainless Steel

Stainless steel work-hardens when a bit rubs without cutting. Once the surface has work-hardened, drilling becomes much harder.

Use a sharp bit designed for stainless steel, cutting fluid, a low drill speed, and firm enough pressure to create chips. If the bit stops cutting, do not continue spinning it in place. Let it cool, inspect the cutting edges, and replace it if it has dulled.

Hardened Steel

Hardened steel is different from ordinary thick steel. A cobalt bit may work on some tough steels, but truly hardened material can defeat HSS and cobalt bits.

Use a carbide drill bit specifically rated for hardened steel and a rigid setup, preferably a drill press. Carbide is very hard but also brittle, so keep the workpiece clamped and the tool aligned. If the steel is part of a tool, fastener, spring, or wear surface, assume it may be hardened unless you know otherwise.

Steel Beams and Structural Steel

A cobalt-alloy twist bit is a practical choice for drilling an ordinary steel beam or thick structural member. For larger holes, an annular cutter used with compatible drilling equipment can be more efficient than forcing a large twist bit through the material.

Whether a beam may be drilled is separate from whether it can be drilled. A load-bearing member may have project, engineering, building-code, or manufacturer requirements that limit where holes can go.

Avoid Heat, Bit Walking, and Rough Holes

Most failed attempts to drill steel come down to heat, movement, or a dull bit.

A bit that spins too fast rubs rather than cuts. The friction overheats the point, dulls the cutting edge, and can harden stainless steel at the hole location. Use the drill’s low gear, cutting fluid, and steady pressure instead of trying to force the job with speed.

A bit that walks at the start usually needs a center-punch mark or a better point design. A split-point, PILOT POINT, or chisel-point bit can help reduce walking.

A bit that suddenly requires much more pressure is usually dull. Extra pressure does not make a dull bit cut effectively.

Titanium-coated HSS bits can be useful for occasional mild-steel work, but the coating wears at the cutting edge. For demanding jobs, choose a bit designed for the material rather than depending on coating color.

Check the Hole and Care for the Bit

Before assembling the project, run through this quick check:

Confirm the hole is in the intended location and the fastener fits without force.
Remove burrs from both faces of the steel.
Check that the workpiece has not bent, torn, or developed a sharp raised edge.
Let the bit cool before handling it.
Wipe off cutting fluid and metal chips, then store the bit dry to help prevent rust.

If the hole is slightly undersized, enlarge it gradually with the next bit size or a step bit. Do not force a bolt through a tight hole, since that can damage threads and distort thin steel.

Frequently Asked Questions

Should You Use WD-40 When Drilling Metal?

WD-40 can provide some lubrication for a light metal-drilling job if dedicated cutting fluid is not available. A purpose-made cutting oil is the better choice for steel, especially stainless or thicker stock, because it is designed to reduce heat and help the bit cut rather than rub. Apply lubricant to the drill point and the drilling area before starting.

Are Drill Bits Steel?

Many drill bits are steel, but the steel matters. HSS bits are hardened tool steel designed to keep a cutting edge at elevated temperatures, while cobalt bits are cobalt-alloy tool steel rather than solid cobalt. Carbide bits are a different, much harder material used for especially hard workpieces.

Can a Cordless Drill Drill Through Steel?

Yes, a cordless drill can drill ordinary steel if it has enough battery power, the correct bit, and a low-speed setting. Clamp the steel, center-punch the location, use cutting fluid, and use a sharp HSS or cobalt bit. A drill press provides better alignment for thick steel, larger holes, and hardened materials.

Do You Need a Special Drill Bit To Drill Through Steel?

You need a drill bit made for metal, not a brad-point wood bit or masonry bit. For common mild steel, choose a sharp HSS twist bit with a steel-ready split point; for stainless steel and harder metals, use a cobalt-alloy bit. Identify the steel first, then match the bit before drilling.