The Best Cobalt Drill Bits, Tested and Reviewed

Hello, my friend, hello again; today we come together to talk about The Best Cobalt Drill Bits, Tested and Reviewed and hope the blog can help you.

When you need to bore through metal, cobalt is the only material that will do. Here’s the drill on the best cobalt bits you can buy.

There aren’t many materials strong enough to put holes in hardened steel. For that kind of strength, the only answer is cobalt alloy drill bits.

These powerful cobalt drill bits for cast iron, aluminum, and even stainless steel are made of a steel alloy of 5 percent to 8 percent cobalt. We researched dozens of cobalt drill bit sets before testing the following picks.

Read on to find out more about our shopping considerations and testing process. This guide will help you find the best cobalt drill bits for turning metal into Swiss cheese.

1. BEST OVERALL: DeWalt Industrial Cobalt Alloy Steel Set
2. RUNNER-UP: Irwin 29-Piece Cobalt Alloy Steel M35 Drill Bit Set
3. BEST BANG FOR THE BUCK: Amoolo 13-Piece Cobalt Drill Bit Set
4. UPGRADE PICK: Drill America Cobalt Jobber Drill Bit Set
5. BEST M42: Bosch 14-Piece Cobalt M42 Drill Bit Set
6. BEST FOR STAINLESS STEEL: Milwaukee 15-Piece Cobalt Red Helix Drill Bit Kit
7. BEST METRIC: Stroton Metric M42 8% Cobalt Twist Drill Bits Set
8. BEST STEP BITS: Milwaukee 3-Piece Cobalt Step Drill Bit Set

Before You Buy Cobalt Drill Bits 

Before deciding to purchase a set of cobalt drill bits for metal, shoppers will want to make sure they know what they’re getting. While these bits can cut a variety of materials, they are specifically designed to cut through hard metals such as stainless steel, cast iron, hard steel, and even titanium. Because cobalt alloy bits are more expensive than conventional metal drill bits, they aren’t economical options for drilling materials like wood or masonry. Before making a purchase, shoppers will want to make sure they’re buying the right drill bits for the job.

In addition, be aware that drilling into hard metal requires a special technique to ensure that the bit cuts into the metal smoothly without overheating. Use a quality drilling lubricant with a high flash point. We used 3-In-One Multi-Purpose Oil for our tests. Also, drill at a slower speed with moderate downward pressure to avoid damaging expensive bits. The smallest bits can safely drill at about 3,000 rotations per minute (rpm), but larger bits should turn no faster than about 1,000 rpm.

How We Tested Cobalt Drill Bits

Machinists, mechanics, DIYers, and crafters value cobalt bits for their ability to drill hard materials and because they can be resharpened. We spent 12 hours testing these drill bit sets. First, we used a drill press to evaluate them for drilling ability in aluminum, cast iron, and stainless steel. Then we resharpened them before performing a second round of drilling tests. (For most products, we used a drill press for each set of holes; however, for two products, we used a drill press and a cordless drill, as noted above.)

For the first round of drilling evaluations, we selected the 1/16-inch, 3/16-inch, and ⅜-inch bits from each set. The test materials included scraps of .25 sheet aluminum, .133 cast-iron pipe, and .065 square tubular stainless steel. We calibrated the drill press rpm to match the bit size and material based on this chart and used 3-In-One Multi-Purpose Oil as a drilling lubricant. We drilled three holes in each of the test materials with every drill bit and then noted penetration speed (aggressiveness), cleanliness of the hole edges, and any noticeable changes from the first to the last hole.

After drilling the first round of test holes (or after the second round for some harder drill bits), we sharpened the ⅜-inch bits with a bench grinder. We held the cutting edge to the wheel for 5 seconds on each cutting edge, once on the coarse grinding wheel and once on the fine wheel, making sure to maintain the 135-degree original tip angle. To evaluate how well the bits responded to resharpening, we drilled another round of three test holes for each bit in the scrap steel.

We tested with an eye out for the best drill bits that might work especially well for specific metals, such as which ones may be best for stainless steel or best for cast iron. While the unique tips on the Milwaukee 15-piece cobalt drill bits proved especially effective at drilling in stainless steel, all of these drill bits would do well boring clean holes into a variety of metals. With that in mind, we assigned awards for each product based more on its features rather than on specific metal uses.

Our Top Picks

After researching more than 40 cobalt drill bit sets, we spent hours testing the following bits on aluminum, cast iron, and stainless steel. Read on to learn how they performed in testing and why we consider them to be some of the best cobalt drill bits around.

Best Overall

DeWalt Industrial Cobalt Alloy Steel Set

See It

When drilling metal, some of the biggest headaches are bits that break, spin in the chuck, and bounce over the metal’s surface. DeWalt addresses all those issues with this set.

Picked as our best drill bit set, this high-grade cobalt and stainless steel enhance the durability of these drill bits, so users don’t need to worry about breaking a bit. A pilot point makes it much easier to get started and eliminates the need for a separate pilot hole. And DeWalt goes with a flat-sided shank to get rid of spinning issues. This 14-piece set includes sizes ranging from 1/16 inch to ⅜ inch.

In testing, the stepped split pilot point allowed the DeWalt cobalt metal drill bits to penetrate the metal quickly without slipping. They maintained a good level of sharpness through the first three holes, but the point was slightly less aggressive by the third hole.

Having two levels on the point made it more difficult to sharpen the bit accurately while maintaining the factory angle, but we managed to shape it up. The final test hole after sharpening came out smooth and clean. We also really liked the 3-flat shank that made these bits fast and easy to assemble into the drill chuck. For the price, these bits make a good all-purpose choice, especially for those who drill metal regularly.

Product Specs

• Number of bits: 14
• Sizes: 1/16 inch to ⅜ inch
• Cobalt value: M35

Pros

• 3 flat sides on the shank for more secure chucking
• Stepped split tip penetrates material more accurately than similar products
• Includes the most commonly used bit sizes for most drilling projects
• Ruggedly built carry case and clear lid with easy bit indexing

Cons

• Stepped split bit is more difficult to resharpen compared to similar drill bit sets

Get the DeWalt cobalt drill bits at Amazon, Ace Hardware, or Lowe’s.

Runner-Up

Irwin 29-Piece Cobalt Alloy Steel M35 Drill Bit Set

See It

Those in need of several bit sizes will want to check out this 29-piece set from Irwin. Sizes for these twist drill bits run from 1/16 inch to ½ inch in 1/64-inch increments. Each bit features a split-point top, which makes starting holes easier. The M35 alloy bits are made from an alloy of steel and 5 percent cobalt for longer life under tough drilling conditions.

As a lot of DIYers can attest, loose bits eventually become lost bits. Irwin knows that, so this set comes with a convenient carrying case that securely indexes all 29 bits into three separate cartridges that fit neatly into a durable and portable rubber molded case.

The Irwin M35 drill bits performed well before and after sharpening—in fact, the bit had barely dulled after the first three holes. With or without a center punch to premark the hole locations, these bits drilled smooth, clean holes. Also, the split point was easy to line up at the proper angle to sharpen on the grinder.

We really liked the bit case for organized storage, although the combined weight of the metal case and 29 bits was heavy—probably best for workshop use. With so many sizes to choose from in 1/64-inch increments, this set would be a great pick for those who need precision drilling for a variety of projects. On the other hand, its premium price may not be worth it for those who would need these bits only for occasional use.

Product Specs

• Number of bits: 29
• Sizes: 1/16 inch to ½ inch
• Cobalt value: M35

Pros

• Split point is easy to resharpen to extend the working life of the bit
• M35 cobalt alloy is compatible with most hard and soft materials
• 29-piece set offers more incremental sizes for precision drilling projects
• Includes a heavy-duty steel carrying case with a tap-and-drill selection chart

Cons

• Premium price compared to other cobalt drill sets on the market
• Heavy carrying case is not ideal for transporting to jobs

Get the Irwin cobalt drill bit set at Amazon, Acme Tools, or Tool Barn.

Best Bang for the Buck

Amoolo Cobalt Drill Bit Set

See It

This 13-piece set from Amoolo comes in at a fraction of the price of other cobalt drill bit sets. This set is durable, with 5 percent cobalt steel alloy, though not as strong as M42 bits, which contain 8 percent alloy. Using a lubricant or cooling water can help extend the life of these bits. Their split-point tips prevent walking and make starting holes easier. Ranging in size from 1/16 inch to ¼ inch, these bits come in a plastic carrying case with labeled sizes.

The Amoolo cobalt drill bits performed as well as some of the top name brands in our tests but cost a fraction of the price. They drilled smooth, clean holes, and the 135-degree split point was easy to align with the bench grinder for sharpening. It bears mentioning, however, that the kit only includes smaller bit sizes in 1/16-inch increments, which makes it ideal for crafting and detailed drilling.

The only downside we found was the flimsy plastic case and foam bit holder: They felt more like shipping materials than parts of a protective carrying case. Still, functionally speaking, we doubt that anyone would know the difference if we replaced some of their Irwin cobalt drill bits with these.

Product Specs

• Number of bits: 13
• Sizes: 1/16 inch to ¼ inch
• Cobalt value: M35

Pros

• Compared to top name brands, offers a budget-friendly price point for heavy-duty drill bits
• Bit sizes are given in both fractions of an inch and in millimeters
• Includes 13 bits in 1/64-inch size increments for precision drilling
• Split point is easy to resharpen for a longer working life

Cons

• Flimsy plastic and foam carrying case compared to those offered by other brands

Get the Amoolo cobalt drill bits at Amazon.

Upgrade Pick

Drill America Cobalt Jobber Drill Bit Set

See It

This set of premium cobalt drill bits from Drill America features 29 pieces that range in size from 1/16 inch to ½ inch in 1/64-inch increments. The gold finish acts as a built-in lubricant to keep heat levels down, making it the strongest drill bit for drilling through metal easier and extending the life of the bit. Each bit is made from high-grade M42 cobalt stainless steel alloy. A split point quickly penetrates hard metals without the need for a pilot hole.

Working with the Drill America M42 drill bit was almost an identical experience to working with the Irwin drill bit set, but this set is made of tougher metal and provides easier access to all of the bits at once. Both sets offer the same size assortment, the same round shank, and 135-degree split-point construction. Drill America’s bits remained noticeably sharper after the first three test holes, so we drilled a second set of three holes before sharpening. Sharpening took slightly longer, but the split point made it easy to align them with the grinder.

The round plastic carry case was more compact and lightweight than the Irwin case and featured a watertight threaded cover, but reading the bit size labels was more difficult. This could be a nice set to keep in the shop or for carrying to project sites.

Product Specs

• Number of bits: 29
• Sizes: 1/16 inch to ½ inch
• Cobalt value: M42

Pros

• M42 cobalt alloy steel bits work harder and last longer than M35 bits
• Split-point tips can be resharpened for a longer working life
• Kit includes 29 bits and 1/64-inch incremental sizes for precision drilling
• Unique round carry case offers fast access to different bit sizes

Cons

• Bit sizes on the carry case rim are not easily visible

Get the Drill America cobalt drill bits at Amazon or DrillsAndCutters.com.

Best M42

Bosch CO14B 14-Piece Cobalt M42 Drill Bit Set

See It

With its M42 drill bits, this set from Bosch is ready to take on the hardest metals. The 8 percent cobalt alloy is more durable than what’s used for M35 cobalt drill bits, giving it longer shelf life. This set’s other features also make drilling through metal a breeze. A split-point tip penetrates metal easily, while a flat shank prevents slipping in the chuck. These Bosch bits have thicker threading than most spiral drill bits, a design that’s meant to remove material more efficiently and decrease the amount of time it takes to drill through metal. This set includes 14 pieces, with sizes ranging from 1/16 inch to ½ inch.

The Bosch cobalt drill bits offer a unique combination of structural features and extra-hard M42 alloy that make them a pleasure to work with. To test this product, we used a cordless drill and a drill press to highlight the difference between precision drill press work and handheld drilling. The cordless drill mostly worked well, but its variable-speed trigger made it more difficult to maintain a slow, precise speed for drilling steel.

Overall though, we really liked the split-point tip and 3-flat shank for secure chucking, smooth drilling, and easy sharpening. As with our other M42 test bits, these held their edge well enough to drill a second set of test holes with the drill press before sharpening. Sharpening was also easy thanks to the split point. For drilling hard, brittle cast iron, the extra control afforded by the design of these bits was especially helpful.

Product Specs

• Number of bits: 14
• Sizes: 1/16 inch to ½ inch
• Cobalt value: M42

Pros

• Split-point bits are easy to sharpen for an extended working life
• 3 flat sides on the shank eliminate slipping in the drill chuck
• M42 cobalt alloy lasts longer and works harder than M35 alloy
• Kit includes the most popular drill bit sizes for general-purpose drilling

Cons

• Bit size labels on the carry case are extremely hard to read

Get the Bosch cobalt drill bits at Amazon, The Home Depot, or Lowe’s.

Best For Stainless Steel

Milwaukee 15-Piece Cobalt Red Helix Drill Bit Kit