9 Best Cobalt Drill Bits for Metal | Sharper Than the Hype

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A 13-bit set with rock-solid 68 HRC hardness that tackles hardened steel and stubborn bolts.

STROTON guarantees the 5% cobalt content by sourcing ore from its own mine—cheaper bits often fake it. The M35 steel is hardened to 68 HRC (Rockwell Hardness Scale, a measure of dent and wear resistance), so these bits chew through stainless steel plate, iron sheet, and cast iron without losing their edge. Owners mention one bit drilled through a hardened 10.9 steel bolt—about as tough a test as a twist drill can face.

You get 13 jobber-length bits (standard-length twist drills) in 1/64-inch increments from 1/16″ up to 1/4″, so precise sizing covers the most common small-to-mid holes. The split point design (a notched tip that bites immediately) and fully ground process suit heavy-duty work like drilling out bolts, studs, and screws. The manufacturer claims 3x heat, wear, and chip resistance plus 3x tool life versus ordinary bits, though real-world results depend on your technique.

The honest trade-off is that cobalt at this hardness is inherently brittle. Owners stress that you need to go slow, use cutting oil, keep firm pressure, clear chips often, and let the bit cool — bend or overload it and it will snap. Used right, these are described as excellent quality that cuts well across several surfaces.

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Five long 3/8-inch bits built to punch through steel plate and keep punching.

This set skips size variety and goes deep on one workhorse size: five identical 3/8-inch by 5-inch bits of M35 cobalt. It’s a deliberate choice for anyone drilling larger holes in steel, stainless, cast iron, or titanium alloy. The pilot point tip (a sharpened point that bites first and prevents slipping) increases drilling speed and eases penetration through hard metal. One owner drilling a go-kart frame reported “hundreds of holes, 1 bit left from 5” through cold-rolled quarter-inch steel—a serious durability flex.

At a 3/8-inch cutting diameter, these bits drill holes 52% wider than the 1/4-inch bits in the RCINDUS set above, so they cover fasteners and structural work that smaller sets simply can’t. The heavy-duty M35 construction gives superior resistance to abrasion and high heat, and the long 5-inch length reaches through thicker material and awkward spots.

Owners consistently praise the cutting performance — bits that “run true” and “work great” on steel with medium drill settings. The durability feedback is mixed, with a few noting the bits are sharp but brittle, especially if you abuse them enlarging holes or skip the lubricant. Treat them with a light touch on a drill press and they’ll reward you.

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Bits so sharp they drilled eight holes in a tractor bucket and stayed just as sharp on the last.

LU&MN’s 10-piece set is the razor-sharp performer of this list, with a fully ground flute design that removes chips efficiently and cuts friction for smoother, more accurate drilling. The M35 steel carries 5% cobalt, and the 135-degree split point self-centers to prevent walking while requiring less pressure — a real advantage when you’re leaning into a stubborn piece of steel. A buyer drilling a John Deere bucket reported one bit handled all 8 holes and “is just as sharp on the 8th as the first.”

The set spans 1/4-inch and smaller, which covers most automotive and fabrication jobs, and the round shank (the smooth end that grips in the chuck) fits a wide range of drill chucks and drill presses. The titanium nitride finish adds a layer of surface hardness and lubricity, helping the bit slide through metal with less heat buildup.

The feedback is strongly positive on performance — bits that “cut right through stainless as long as you don’t overheat” and that outperform other advertised-metal bits that only dented the workpiece. The durability discussion is where opinions split: some report bits that break quickly if overheated, while others find them rugged and long-lasting. The rule for stainless is the same everywhere: keep it cool and it will cut.

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A rugged indexed case and three-flute design make this the set you’ll actually keep organized.

SALI’s 10-piece set earns its keep on two fronts: it cuts through hard metal and its storage case is genuinely well thought out. The M35 high-speed steel contains 5% cobalt for wear resistance, and the fully ground spiral groove clears chips quickly to reduce friction and heat for faster, cooler drilling. The 135-degree split point and straight shank prevent walking, so you can start holes accurately without a center punch. One owner described cutting through galvanized fence posts “like butter.”

The 10 bits are 1/4-inch and smaller, and the molded case has sizes printed on the lid so you grab the right bit without rummaging. What’s unusual here is the connectable accessory storage system — the case links to other SALI cases to consolidate your toolkit into one space-saving stack.

The quality consensus is strong—a retired industrial tool salesman called these “as good as any drill bit I have ever used.” The honest caveat is durability on the hardest jobs: one owner drilling stainless bolts burned through three bits in 40 minutes, though they conceded the value is still good for softer metals. Use oil and moderate speed on stainless, and these will serve you well.

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Three aggressive half-inch bits that tore through A36 steel in about one second flat.

This is the set for anyone who needs genuinely large holes fast. The three 1/2-inch (12.7mm) bits are made from cobalt 5% high-speed steel, and fully ground processing makes the surface smoother, so friction drops and cutting speed climbs. Customers note these are “extremely sharp and aggressive,” with one drilling through 1/4-inch A36 steel in roughly one second versus 15-20 seconds for a leading-brand M35 set—a 15x speed gap that changes how a long job feels.

The 135-degree split point self-centers on the workpiece, boosting cutting speed and preventing the skating common on slick metal. Manufacturing follows ANSI B94-11M (the American standard for twist drill dimensions), so you’re getting a properly toleranced tool, and the three bits ship in a compact plastic case.

Durability gets a split verdict: one owner found the first bit wouldn’t cut their very hard steel while the second drilled four holes fine, and another reports the flutes scuff but the edge stays sharp through eight holes. The consensus advice is a light touch with cutting oil — these cut so aggressively they’ll grab if you lean on them.

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A 17-bit range from 1/16 to 1/2 inch that cut stainless like a hot knife through butter.

This is the complete-coverage set—an experienced woodworker called it “the very best and highest quality drill bit set I have ever owned.” The 17 bits run from 1/16-inch up to 1/2-inch with duplicates of the most-used sizes, and each one is M35 cobalt steel at 68 HRC (Rockwell Hardness Scale) with the cutting edge ground three times for high hardness and heat resistance. On stainless steel, owners describe holes that cut “like a hot knife through butter”—including a smooth pass through 5/8-inch plate.

The 135-degree split point self-centers to prevent walking, and the sharp edge cuts clean metal ribbons instead of grinding. The range covers everything from tiny pilot holes to half-inch structural work, with the 2-piece duplicates on 1/16″, 3/32″, 1/8″, and 1/4″ sizes covering the bits you’ll reach for most.

The manufacturer claims these run two to three times faster than standard bits, and their longevity improves cost-per-hole value. Durability feedback is mixed — some report breakage on very hard materials — but the overwhelming pattern is that this set stays sharp, cuts clean, and gets the job done where other brands failed.

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Twenty-five metric bits from 1mm to 13mm in a metal case that owners genuinely rave about.

If you work in metric, this set eliminates the fraction-to-millimeter guesswork entirely. The 25 bits step through every millimeter from 1.0mm to 13.0mm, so you always have the exact size you need rather than rounding to the nearest fraction. Each bit is M35 cobalt steel with a 135-degree point tip and twist design for faster cutting, self-centering to prevent walk-off, and quicker chip removal. Shoppers say these “cut through metal like butter” and stay sharp even after heavy use.

The storage case is a genuine highlight—it’s made of painted metal rather than cheap plastic, and owners describe the whole kit as “perfectly decent at an excellent price point.” The molded size indexes on the case make sorting and grabbing the right bit fast, and the hardened, polished inserts improve sharpness for precise cutting without wobble.

The durability story is honest: one owner drilling six holes in quarter-inch mild steel found the bit dulled mid-first-hole, but after a light sharpening it finished the job and five more without re-sharpening. The maker notes these aren’t for quenched bolts, and the guidance is consistent — cutting oil, slow speed, and frequent chip clearing on stainless steel keep the bits happy.

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The M42 8% cobalt set built to National Aerospace Standard 907 for the toughest alloys on earth.

This is the specialist’s choice. Drill America’s 15-piece set uses M42 cobalt with 8% cobalt content — the highest grade on this list — and it’s manufactured to National Aerospace Standard 907, a rigorous spec for aerospace-grade tooling. The extra cobalt boosts red hardness, enabling cutting speeds up to 30% faster than standard high-speed steel drills. It’s the set owners reach for on Inconel, stainless steel, and titanium — materials that eat lesser bits for breakfast.

The 15 bits span 1/16″ through 1/2″ in 32nds increments, covering everything from small precision holes to half-inch structural work. Each bit has a 135-degree split point (a notched tip that self-centers) for fast penetration and precision drilling. In practice, buyers report drilling 20 holes in half-inch steel with minimal wear. The most common complaint: a couple of smaller bits arrive slightly chipped from the factory—though they still cut through steel fine with cutting oil.

Durability is the honest discussion point here. The summary notes breaking multiple bits within four months for some owners, but the counterpoint is consistent: used properly with the right RPM and cutting oil, these outlast store-bought sets. One owner accidentally chipped a tip in hammer mode, and Drill America sent a free replacement — service that backs the premium price.