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Drilling into metal is where standard drill bits go to die. The heat, the hardness, the constant skating across the surface — it chews up cheap HSS (high-speed steel) bits in seconds. If you are trying to punch through stainless steel, cast iron, or even hardened alloys, you need a bit that is part of the alloy itself, not just coated. Cobalt steel bits have cobalt mixed into the metal, so they stay hard and keep cutting long after ordinary bits have gone dull.
I’m Mohammad Maruf — the founder and writer behind WellFizz. This guide is built by comparing the manufacturers’ published specifications and the patterns across verified customer reviews, so you get each pick’s real strengths and trade-offs instead of marketing spin.
Whether you are a metal fabricator, a mechanic, or a weekend DIYer, finding the right set of cobalt drill bits for metal means understanding the difference between a bit that fights you and one that cuts straight and clean on the first try.
Our Picks at a Glance
How To Choose The Best Cobalt Drill Bits For Metal
Not all drill bits sold as cobalt are the same. The key difference is whether the cobalt is a coating that wears off, or if it is a percentage of the actual steel alloy. Here is what to look for to keep your drill from burning up on the first hole.
Look for 5% Cobalt Content
Real high-speed steel (HSS) cobalt bits have a small percentage of cobalt — usually 5% — blended into the metal. This makes the bit harder at high temperatures, so it holds its edge much longer when drilling into stainless steel, cast iron, or other tough alloys. Bits with “cobalt” only as a surface coating will lose their hardness quickly once the coating wears away.
135-Degree Split Point is a Must
A standard 118-degree point tends to “walk” or slide across smooth metal when starting a hole. A 135-degree split point is flatter and has a self-centering shape that bites into the metal immediately, so you do not need to center-punch every hole. This design is essential for drilling into metal without the bit skidding and scratching your workpiece.
Consider the Shank Design
Most cobalt bits come with a straight round shank (the part that goes into the drill chuck) or a three-flatted shank (a shank with three flat sides). A three-flatted shank gives your chuck a better grip, preventing the bit from spinning inside the collet under heavy load. This is especially important when using keyless chucks (chucks you tighten by hand) on modern drills, as round shanks can slip when you apply high torque.
Quick Comparison
| Model | Best For | Pieces | Min Bore Diameter | Weight | Amazon |
|---|---|---|---|---|---|
| BECOLLO 3-Piece★ Best Overall | Big 1/2″ hole jobs | 3 | 0.5″ | — | Amazon |
| HIDOTOL 115PCSAlso Great | Complete workshop kit | 115 | 1/16″ | 7.5 lbs | Amazon |
| Irwin 15-Piece (316015) | Premium daily driver | 15 | — | 11.2 oz | Amazon |
| WildBossy M35 20PCS | Versatile mid-range set | 20 | 0.06″ | 15.2 oz | Amazon |
| ZNXIMER 16PCS | Budget-conscious steel drilling | 16 | 1/16″ | — | Amazon |
In‑Depth Reviews
1. 1/2 Inch Cobalt Drill Bit Set, M35 Jobber Length Twist Drill Bits, 3 Pieces
Our pick — over 4.5★ from 750+ verified ratings; the strongest balance of quality and price.
Three identical 1/2″ cobalt bits for when you need to drill a big hole and keep drilling.
This BECOLLO set is a specialist tool: three jobber-length (standard length) cobalt bits, each with a 1/2-inch (12.7mm) cutting diameter. At 0.5 inches, the minimum bore diameter is 0.5 inches versus the WildBossy set’s 0.06-inch minimum, meaning these bits are built for one job — punching large-diameter holes through thick steel. The 5% cobalt HSS material resists the heat that builds up during larger cuts, and the 135-degree split point keeps the bit from walking on a smooth surface. One reviewer noted drilling 11 holes through thick steel with these 3 bits, noting that a competitor’s 2 bits failed on 1 hole. Another used them to drill through F150 leaf springs (hardened steel) but stressed keeping the RPM low and using constant oil. The bits come in a plastic case for storage.
Hard-target specialist: Three bits at the same size let you rotate them as they heat up, which is smart for production metal drilling.
Narrow use case: You get no smaller bits, so this is only useful if you specifically need 1/2″ holes in hard metal.
This is for you if: You routinely drill 1/2″ holes through steel plate, structural beams, or leaf springs and want backup bits ready. For general work requiring a variety of hole sizes, the HIDOTOL 115-piece set is far more versatile.
2. HIDOTOL 115PCS Cobalt Drill Bit Set M35 HSS
This 115-piece set covers every fractional, letter, and wire-gauge size from #60 to 1/2″ in one organized metal case.
Running out of the right bit size mid-job kills productivity in any metalworking shop. With 115 pieces, you have the exact bit for almost any fastener, tap, or clearance hole without guessing. Each bit is M35 cobalt steel with a 135-degree split point that self-centers on stainless steel, cast iron, and titanium alloy. At 7.5 pounds, this heavy-duty kit feels substantial in the shop. Buyers report the bits are “very sharp and durable,” drilling through harder material than regular drills could.
Total coverage: You get every fractional, letter, and wire-gauge bit from tiny #60 up to 1/2″ in one organized metal case.
The catch: At 115 bits, some buyers may never use more than a fraction of them, and the weight makes it less portable than a small index case.
For the pro or serious DIYer: One kit to cover every metal-drilling scenario for years. If you only need a few sizes, a smaller set saves shelf space and money.
3. Irwin Tools IRWIN Drill Bit Set, Cobalt Alloy Steel, 15-Piece (316015)
Irwin’s redesigned tip keeps cutting long after cheaper bits quit, and the three-flatted shank stops the bit from spinning in your drill.
Irwin’s 15-piece set is built around a cobalt alloy steel material (not just a coating), and it shows in the reviews. One buyer used these with an old Milwaukee drill and cutting fluid to drill 5/16″ and 3/8″ holes through 3/8″ steel plate, calling it “excellent value.” The three-flatted shank (a shank with three flat sides) gives your keyless chuck a far better grip than a round shank, so the bit does not spin under heavy load. At 11.2 ounces it is noticeably lighter than the WildBossy 20-piece set, which weighs 15.2 ounces, making this set easier to carry to a job site. The stackable plastic case with a clear lid keeps everything organized and visible. Irwin redesigned the tip to promote longer life, and the 135-degree cutting angle helps prevent walking on smooth metal surfaces.
Real-world performance: “Used with cutting fluid and old Milwaukee drill to drill 5/16″ and 3/8″ holes in 3/8″ steel plate,” reports one verified buyer.
Trade-off: You do not get a 1/2″ bit in the set, so it skips the largest common size that the WildBossy kit includes. It is also the priciest option per piece here.
Choose the premium Irwin over the budget ZNXIMER if: You need a compact, durable set from a well-known brand that handles stainless and steel plate reliably. Do not buy it if your work regularly calls for a 1/2″ hole — you will need a separate bit for that.
4. M35 Cobalt Drill Bit Set 20PCS (1/16″-1/2″) High Speed Steel Jobber Length Drill Bit Kit
A well-rounded 20-piece kit that covers the most common sizes without emptying your wallet.
This set from WildBossy includes sizes from 1/16″ up to 1/2″, with duplicates of the smaller sizes (like two each of 1/16″, 5/64″, 3/32″, and others) since those are the ones most likely to snap under hard use. It is made from M35 cobalt steel, which the maker claims can measure up to 67 Rockwell hardness (a scale for material hardness). The 135-degree split point and titanium surface (Ti surface) finish help reduce walking and friction. One verified buyer who got these specifically for thin stainless steel reported, “They worked really well. They have two straight sides on the bottom so they don’t spin in my drill.” Another review noted the three-flatted shank design keeps the bit from slipping in the chuck. At 15.2 ounces, this kit is heavier than the Irwin set, but you get five more pieces and the largest bit goes up to 1/2″, which the Irwin set lacks.
Solid mid-range choice: Includes a 1/2″ bit and duplicate small sizes — practical for shop use where you often drill standard holes.
Watch out for: Some buyers reported occasional dull bits or one snapping on the first use, so check each bit before a critical job. The HIDOTOL 115-piece set has more uniform review consistency.
Best for: The home mechanic or metalworker who wants a broad size range and good cobalt quality at a mid-range price, and specifically needs the 1/2″ size that the Irwin set omits.
5. ZNXIMER Cobalt Drill Bit Set, Metal Drill Bit Set for Steel, 16PCS 1/16″ to 3/8″
A budget-friendly 16-piece set that handles steel and even wood with real 5% cobalt steel.
ZNXIMER’s set covers the most used sizes from 1/16″ to 3/8″ in a plastic index case, with duplicates of the smaller bits (1/16″, 5/64″, 3/32″, and 1/8″ each come with two). The M35 high-speed steel with 5% cobalt is the same basic material found in pricier sets, so you get genuine heat and wear resistance when drilling into stainless steel, cast iron, or hard alloys up to HRC38° (a hardness rating of 38 on the Rockwell C scale). The 135-degree split point helps you start straight without a center punch on most surfaces. A buyer reported, “Set drilled remaining 24 holes through wood and steel trailer frame using only 2 bits,” and noted a flat spot on the shank that prevents spinning in the chuck. That is a smart design touch often missing at this price. It is note the ZNXIMER requires attention to speed and heat control on tougher metals — several reviewers found it could not handle hardened steel.
Everyday value: For the price of a single 1/2″ cobalt bit, you get 16 bits that work on mild steel, wood, and aluminum.
Its limit: Hardened steel above HRC38 will defeat these bits — the material simply is not hard enough for spring steel or hardened bolts. For those jobs, the WildBossy or Irwin sets are a better bet.
Grab this if: You want a cheap, reliable set for general metalwork and are not drilling into hardened steel or thick stainless.
Pass if: You need to drill into hardened alloys often.
Understanding the Specs
M35 Cobalt Steel
M35 is a specific grade of high-speed steel that contains 5% cobalt and also molybdenum. The cobalt helps the steel stay hard even when it gets hot from friction, which is exactly what happens when you drill into stainless steel or cast iron. This means the cutting edge does not soften and go dull as quickly as it would with standard HSS. Bits labeled M35 are a reliable standard for tough metal drilling.
135-Degree Split Point
This refers to the angle and shape of the tip of the bit. A 135-degree split point is flatter than a standard 118-degree point, and the tip has a split that cuts into the metal as you start drilling. This helps the bit self-center, so it does not slide or “walk” across the surface of smooth metal. It is a significant upgrade for drilling into metal without center-punching every hole.
FAQ
Can cobalt drill bits drill through hardened steel?
What is the difference between cobalt drill bits and titanium-coated bits?
How do I keep a cobalt drill bit from breaking?
Is a 3-flatted shank better than a round shank for a keyless chuck?
What sizes do I actually need for metal drilling?
Can I use cobalt drill bits on wood or plastic?
Should I use cutting fluid with cobalt drill bits?
What does “jobber length” mean for a drill bit?
How many pieces should a good cobalt drill bit set have?
Final Thoughts: The Verdict
For most people, the cobalt drill bits for metal winner is the HIDOTOL 115-piece set because it offers an class-leading size range in a durable metal case, covering every fractional, letter, and wire gauge size. If you want a more portable kit for the shop with a trusted brand and a grip-friendly shank, grab the Irwin 15-piece set. And for a budget-friendly option that still uses real 5% cobalt steel, the ZNXIMER 16-piece set is tough to top for everyday metal drilling.
How We Picked
We do not accept paid placement. Every pick is matched to a real buyer and a real use-case; we do not hands-on test units.
Sources & Methodology
Specifications: manufacturer listings and product documentation. Review insights: verified customer reviews, as of July 2026. Pricing: not shown on this page (it changes often); check the current price via the retailer link.
As an Amazon Associate, WellFizz earns from qualifying purchases. This does not affect which products we feature.
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Mo Maruf
I created WellFizz to bridge the gap between vague wellness advice and actionable solutions. My mission is simple: to decode the research and give you practical tools you can actually use.
Beyond the data, I am a passionate traveler. I believe that stepping away from the screen to explore new environments is essential for mental clarity and physical vitality.