Best Cobalt Drill Bits Tested: 11 Brands Put Through Mild Steel, Spring Steel, and Torture

Introduction

Drill bit makers love big durability claims. Some brands say their bits last 15 times as long as the competition. That raises a fair question: can an $11 set of bits actually keep up with a set that costs $200?

To find out, eleven brands went through three tests: drilling speed through half-inch mild steel, endurance drilling through hard spring steel with back-to-back attempts, and a breaking-strength test to see which bits survive the most torque. All bits were purchased independently so the results stay unbiased.

How the Bits Were Tested

The speed tests used a half-horsepower drill press with a weighted pulley system delivering roughly 175 pounds of downward force, cutting oil on every hole, and an RPM matched to the bit size per the drill press speed chart. For spring steel, the RPM dropped to 340 and the force increased to around 220 pounds. Breaking strength was measured in inch-pounds by twisting each bit until it failed.

A note before the individual results: one additional brand, sold as an M42 cobalt bit under the “LW” label, struggled badly on mild steel, chipped badly, and was far too brittle to compete. It is not recommended here.

DeWalt High-Speed Steel Drill Bits

At around $11 to $15 for a 14-piece set, the DeWalt high-speed steel bits are the budget pick of the group. They use a 135-degree split point, a no-spin shank with flats, and DeWalt claims a very strong core to resist breaking. They are made in Thailand.

On mild steel, they drilled the second-fastest hole of the entire field at 10.53 seconds, finished the test looking new under the microscope, and broke at a solid 191 inch-pounds. On spring steel they managed one hole before wearing out, but for occasional use on softer metals they are tremendous value.

Sommerata Cobalt Drill Bits

Priced at about $15 for 14 bits, the Sommerata bits are M35 cobalt with a 135-degree split point, designed for hard materials like stainless steel, cast iron, and high-temperature alloys, as well as softer materials like plastics and wood. They are made in China.

The Sommerata was decent but consistently slow: 15.84 seconds on mild steel, 44.6 seconds on the first spring steel hole, and mid-pack after back-to-back runs. Breaking strength came in at 173 inch-pounds, the lowest among the mainstream cobalt brands tested.

Irwin Cobalt Drill Bits

At $28 for 15 bits, the Irwin set has a reputation for above-average performance at a below-average price, and it largely held up here. The bits use a 135-degree split point and are made in China.

They drilled mild steel in 11.41 seconds with no visible damage, led the field at one point on spring steel with 24.9 seconds, and stayed competitive in the back-to-back rounds at 14.45 seconds. The weak spot is strength: the Irwin broke at just 88 inch-pounds, among the lowest of all bits tested.

DeWalt Cobalt Drill Bits

At $29, the DeWalt Cobalt bits cost more than twice the high-speed steel version, so the question is whether they are twice as good. These use a Pilot Point tip, claim four times the life in stainless steel, and are made in China and Germany, with the 3/8-inch test bit coming from Germany.

They finished mild steel in 11.15 seconds with no visible damage, took the lead on the first spring steel pass at 22.72 seconds, and stayed fast in round two at 14.34 seconds. Breaking strength was 168 inch-pounds, better than the Irwin but not exceptional. One caveat: the Pilot Point tip makes these very difficult to sharpen.

Bosch Cobalt Drill Bits

At $34 for 14 bits, the Bosch set is an M42 cobalt bit with an 8% cobalt alloy and a claimed ten times the life, plus a thick web helix design for extra stability in tough applications. They are made in China, and affordable M42 bits are genuinely hard to find.

The Bosch drilled mild steel in 11.41 seconds looking like new, stayed on pace through spring steel at 14.6 seconds, and produced the standout result of the strength test: it broke at 215 inch-pounds, second strongest overall. For the money, this is the best balance of speed, toughness, and price in the field.

Milwaukee Cobalt Drill Bits

The Milwaukee set runs $40 for 15 bits and brings an unusual variable helix flute that starts at an aggressive 35-degree helical angle and ends at 15 degrees for rapid chip removal. Milwaukee claims 15 times the life versus black oxide bits. They are made in China.

Milwaukee was the fastest non-sharpened bit through spring steel in the endurance rounds at 19.25 seconds and removed chips visibly faster than most. On mild steel it managed 12.55 seconds, and breaking strength was a good 187 inch-pounds. Like the DeWalt Pilot Point, though, these are very hard to sharpen once dull.

Warrior Cobalt Drill Bits

The Warrior set, sold at Harbor Freight, costs $70 for 29 bits and uses a 135-degree split point cobalt design made in China.

It was slower than average on mild steel at 15.12 seconds but respectable on spring steel, and remarkably, after suffering a very large chip, the damaged edge kept cutting at nearly its original speed, finishing the third round in 15.79 seconds. Strength was below average at 141 inch-pounds.

Cle-Line Cobalt Drill Bits

At $76 for 15 drill bits, the Cle-Line bits are 135-degree cobalt split points made in the USA, which is notable at this price.

Cle-Line drilled mild steel in 10.99 seconds with no visible damage, and it was consistently fast in the endurance rounds at 23.8 and 20.6 seconds, though it lost speed in the final round. It gave up earlier than average in the strength test at 121 inch-pounds, so its strength is speed, not toughness.

Century Drill and Tool Cobalt Bits

The Century set costs $80 for 29 bits, uses 135-degree cobalt split points, and is designed for hardened metal, stainless steel, cast iron, wood, and plastic. It is made in China.

Century was one of the quiet overachievers: 11.2 seconds on mild steel, then the fastest back-to-back spring steel run of the whole field at 12.7 seconds, finishing just behind the much pricier Viking. The trade-off is strength, breaking at 131 inch-pounds, lower than average despite the fast drilling.

Drill Hog Drill Bits

At $140 for 29 bits, Drill Hog is a premium solid M42-plus cobalt bit made in the USA, with a 135-degree split point to prevent walking and three flats on the shank to prevent spinning in the chuck.

The name fits: it has a big appetite for metal. Drill Hog ran 10.63 seconds on mild steel, placed third in the endurance rounds, and was third strongest at 212 inch-pounds. Its average finish of 3.4 placed it near the top of the overall standings.

Viking Drill and Tool Bits

At $200 for 29 bits, the Viking set carries the highest expectations and the highest price. It is an M42 cobalt bit made in the USA with a 135-degree split point for accurate centering.

Viking delivered the fastest mild steel hole of the test at just under 10 seconds, stayed at the front through both spring steel rounds with 12.65 seconds in the final run, and posted the best average finish of 3.4. Strength was only average at 157 inch-pounds, and the price is steep, but as an overall package it finished first.

Test Three: Breaking Strength

Twisting each 6.5 mm bit until failure sorted the field decisively. Century’s Sentry line, at $150 for 29 bits with a 5% industrial-quality M35 cobalt construction, was the strongest of all at 225 inch-pounds despite being slower than average in drilling. Bosch followed at 215, then Drill Hog at 212, DeWalt high-speed steel at 191, Milwaukee at 187, and the brittle LW at 181.

At the bottom, Irwin failed at 88 inch-pounds and Century’s titanium-coated RoBi style bit at 92, so fast drilling clearly does not guarantee a tough bit.

Buying Advice

The Viking Drill and Tool set finished with the best overall average, but overall rankings are not the same as value. For occasional use on softer metals, the DeWalt high-speed steel set at around $11 is the easy recommendation. For anyone who wants the best balance of price, speed, and strength, the Bosch M42 cobalt set at $34 is the standout pick.

One practical consideration: if you plan to sharpen your own bits, avoid the DeWalt Cobalt and Milwaukee sets, since their Pilot Point tips are very difficult to regrind. And if maximum breaking strength matters more than speed, the Sentry line at 225 inch-pounds is the strongest tested.

Conclusion

The most expensive set does not automatically win every test, but the Viking Drill and Tool bits earned their first-place average finish honestly. The real story is value: the $11 DeWalt high-speed steel bits nearly matched the $200 Viking on mild steel, and the $34 Bosch set delivered near-top speed with the second-best breaking strength. Match the bit to how often and how hard you drill, and there is a clear winner at every budget.