We already wrote our opinions on the best drill bits overall—covering wood, metal, concrete, and more. In this go-around, we wanted to identify the best drill bits for metal applications. That includes hardened steel, stainless steel, aluminum, and more. We even wanted to see which drill bits worked well for drilling out hardened bolts as you might find in an engine block. People also ask us about bits that handle drilling through rebar. These are the bits we turn to and should steer you in the right direction.
Best Drill Bits for Hardened Metal or Steel
Clearly, the best drill bits for hardened metal or steel come with a cobalt blend. These cobalt drill bits use an alloy including 5%–8% cobalt. This cobalt makes up part of the steel blend, so the hardness of the bit doesn’t wear off with a coating (like titanium bits). It runs throughout the entire bit.
You can also sharpen these bits—another huge advantage. That matters once you realize cobalt drill bits cost significantly more than other types of twist drill bits. Unlike black oxide or titanium bits, you want to reserve these bits for when you actually need them.
When drilling a hole with a cobalt bit, add a drop of oil on the metal to keep the cutting edge cooler as it cuts. You also want to consider placing some wood underneath the steel if possible. This lets you cut cleanly through the material and not strike a surface below which might dull the cutting edge.
What Do We Mean By Hardened Steel?
When we talk about drilling in hardened steel, we mean medium or high carbon steels typically made using a heat-treatment and tempering process. Hardened steels are durable and can be wear-resistant, corrosion-resistant, and abrasion-resistant. Much of the steel materials that we see used in mechanical engineering, energy generation, and transportation are basically hardened steel. The best drill bits for metal could be designed for these hardened steel applications or they might be optimized for speed in softer carbon steels.
Stainless steels are steel alloys consisting of at least 10.5% chromium and there are different grades. Because of rust and stain resistance, good luster, and low maintenance, it has many commercial uses including cookware, cutlery, home appliances, construction fasteners, and surgical instruments.
However, whatever differences there are between the outer look or chemical composition, both hardened steel and stainless steel are quite difficult to drill into. Using a drill press is often the best way to get quality results.
Our best drill bits for hardened steel include the following:
Best Drill Bits for Hardened Steel
Drill America D/A29J-CO-PC 29-pc Cobalt Set
Drill America makes M42 cobalt bits that held up really well in drilling through anything we threw at them. After testing with a multitude of materials, we selected their jobber bits as our best drill bits for hardened steel.
The bits feature the expected 135° split point, which gives you a nice, steady, and productive drilling speed. The jobber length bits work really well in cordless drills for onsite drilling. They come manufactured to the National Aerospace standard 907. Because of how hard they are, you can drill up to 30% faster than you can with conventional M2 high-speed steel bits. Drill America also doesn’t grind down the shafts on its larger bits—so you get more rigidity, but you also need a 1/2-inch chuck to drive them.
Use these bits when drilling tough, high tensile strength materials like stainless steel—or even titanium. We opted for the D/A29J-CO-PC kit. It includes 29 bits in a shatterproof case. The round case makes it simple to remove the exact bit you need.
Pick up the Jobber Length Drill America D/A29J-CO-PC kit for just $106.
Irwin Cobalt M-42 Metal Drill Bits
We have more on these bits below, but we love the solid design and the convenient case. They did very well in steel and kept a sharp edge after drilling a large number of holes.
The 29-piece kit runs about $100.
Best Metal Drill Bit Set
Irwin 29-piece Cobalt M-42 Metal Index Drill Bit Set
If you plan on drilling hardened metal or steels, we love the Irwin 29-piece M-42 Cobalt bit kit as our the best metal drill bit set. Honestly, it’s not the fastest drilling bit that gets it our nod. It has to do with the use of M42 high-speed steel and its excellent case.
Many less expensive cobalt drill bits use M35 steel which has a 5% cobalt blend. M42 steel uses an 8% cobalt blend. This gives it a greater hardness. It also lets you drill at higher speeds than M35. Irwin actually sells an M35 cobalt set if you don’t plan to drill hardened steel.
Which brings us to the case. If you do a lot of drilling—the case your bits come in matters. Accessing bits can be frustrating (we’re talking to you Milwaukee!) or hugely successful—like with this Irwin three-tier swing case. We love the easy-access bits, and you can easily tell the sizes from the front of each bit. Overall, this kit gives you the best drill bits for metal applications of all kinds.
Some other great options include:
Drill America D/A29J-CO-PC 29-pc Cobalt Set
The Drill America D/A29J-CO-PC includes 29 bits in a shatterproof round case. They make these bits with M42 cobalt steel so they drill really well without heating up quickly. They also seem to hold an edge and stay sharp even after dozens of drilled holes. The round case makes it simple to remove the exact bit you need. Pick up the set for $106.
Irwin 29-piece Cobalt M-35 Metal Index Drill Bit Set
The Irwin 29-piece Cobalt M-42 Metal Index Drill Bit Set performs very similarly to the M42 set. With a bit less cobalt in the steel blend, it just heats up a bit more quickly. You get the same great case. The trade-up is cost. You can get this set for just $111.
Best Drill Bits for Stainless Steel
We have great news for anyone looking for the best drill bits for stainless steel. The same bits you use on hardened steel work on stainless. Hardened steel is a medium of high-carbon steel that gets heat-treated, quenched, and finally tempered. Stainless steel alloy includes chromium (at least 10%) and nickel to make it corrosion-resistant. As a low-carbon steel, stainless steel has a natural hardness that comes without traditional hardening.
Drilling stainless takes a strong bit—the same cobalt bits we recommend above. With that said, stainless can actually harden up as it heats—so drilling slowly often helps you get through the material more efficiently. Use cutting oil or similar lubricant when drilling into stainless and apply enough pressure to see a steady removal of material. Even the best drill bits for stainless steel heat up over time, so be prepared to monitor heat buildup.
Best Drill Bits for Steel (Carbon Steels)
Milwaukee Red Helix Cobalt Drill Bits
Listed in our best drill bits article, Milwaukee Red Helix cobalt bits use a variable flute design that clears away debris quickly. How quickly? About 30% faster than most other 135° split-tip bits we tested against. Their unique design not only helps them drill efficiently, but it also aids in cooling. The trade-off is that these bits thin out more towards the tip. Milwaukee countered this by making them a bit shorter than some others we’ve seen. However, they also extended the flutes lower towards the shaft. The result is a more compact bit with a similar drilling depth.
The 135° split point tip helps when starting your hole and larger sizes feature a Chip Breaker—a groove at the midpoint of the cutting edge that further reduces heat buildup. We love how quickly these bits drill and also how well they remove steel in tight, efficient spirals. The combination of the unique cutting head and the flute design landed these as our best drill bits for steel—particularly carbon steel.
Lacking a 1/4″ hex, use these in your drill or drill press when you need them for thicker, harder metals.
Thanks to the cobalt steel blend, plan on sharpening these when the tips grow dull from use. The value of this kit makes these the best drill bits for steel.
DeWalt Industrial Cobalt Pilot Point Drill Bits
We love the build quality on the DeWalt cobalt pilot point drill bit set. It has a tapered core that gradually adds stiffness to the bit as it gets closer to the base. If you plan to cut stainless, give these bits a shot—they won’t disappoint and make truly clean holes in hardened steel.
This 29-piece kit runs about $100.
Best Drill Bit for Rebar
Diablo Rebar Demon Bits
Sometimes you need to drill through steel…but that steel is buried in concrete. For those applications, you need something like the Diablo Rebar Demon SDS-Max and SDS-Plus bits. We like the design better than Bosch Rebar Cutters because you use the same bit to drill the hole and penetrate the rebar. With Bosch, you drill using rotary hammer mode, switch to the Rebar Cutter in rotary-only mode, and then return to your original bit to finish the hole.
These bits drill quickly through concrete then continue right through rebar. You really can’t find much else on the market that competes at this point, so it’s an easy recommendation for productivity. We believe in charging your accessories to the job—so if a simple bit can save you time and money, it’s a huge win in our book.
Bosch Rebar Cutter SDS-Max Bits
As we mentioned above, Bosch Rebar Cutter bits present a viable option, but they slow you down when working. These bits should last a good while since they only cut the metal of rebar, but we prefer a single cutting solution overall. Shop Bosch Rebar Cutters here.
Best Hole Saws for Metal Drilling
Milwaukee Hole Dozer Carbide Hole Saws
The Milwaukee Hole Dozer with Carbide Teeth really wins for metal drilling. It can tackle stainless steel and certainly anything softer or milder than that. These are the best hole saws for metal drilling that electricians, HVAC, and/or MRO Pros can use.
Because they work effectively in both metal and wood, any Pro looking for a general-purpose set of hole saws should quickly fall in love with their productivity. It vastly outperforms bi-metal blades and tackles those materials carbide wood hole saws can’t (or shouldn’t) touch.
Best Step Bits for Metal
Irwin Unibit Cobalt Step Bits
Our team grabs Irwin Unibit Cobalt Step Bits for any quick thin metal drilling applications. The cobalt blend gives these bits a much longer life. Since step bits are both expensive and extremely difficult to sharpen, we like them to last as long as possible.
Irwin gives these bits a Speedpoint tip. It helps get the hole started quickly and reduces wandering. We also have to admit these became our best step bits for metal in part because Irwin laser-etched the measurements right on the inside of the flute. They don’t wear off quickly like other bits we’ve used.
Pick up a 3-piece kit for $60
Milwaukee Step Bits
Several step bits make for viable solutions for electricians and others looking to drill through sheet metal and thicker materials. While we favor the Irwin Cobalt models above, the dual-fluted Milwaukee Step Bits come in handy configurations to tackle common job site needs. You can get these titanium aluminum nitride-coated bits in various kits from $90-$182.
Diablo Step Bits
Diablo step bits promise twice the cutting speed and up to 6X longer life. They attribute this, in part, to a precision CNC grinding process. We like the 132° split-point tip that all but eliminates the need for pre-drilling. You can get them in sizes from 1/2 to 1-3/8 inches. Pricing for each bit ranges between $23.99 and $50.99.
What are the Best Drill Bits for Metal Made of?
Drill bits made with a Titanium nitride coating resists corrosion and friction. It beats black oxide in that it increases surface hardness and does a better job reducing heat while drilling through metal. For metal drilling, we definitely put these as the bare minimum.
With titanium nitride, you have to remember it only coats the bit. As the coating wears off the cutting edges, you pretty much have to replace them. Don’t use these bits for drilling hardened steel or stainless—not if you want them to last.
Cobalt (Steel Blend)
Our best Cobalt drill bits for metal drilling are made from an alloy of 8% cobalt (M42). You can also find these bits with a 5% cobalt blend (M35). Since the cobalt is blended into the steel, it doesn’t wear away like a titanium or black oxide coating. That also means you can sharpen them before having to replace them. This helps save money when you buy these more expensive bit sets.
Cobalt bits are our go-to for drilling through metal—particularly hardened steels and stainless steel.
Best Drill Bits for Metal, But What About…?
We probably missed something along the way—we get it. At some point we have to draw the line and finish the article. With that said—let us know what you think the best drill bits for metal are. Leave a comment below—especially if you have a “hero” story about how a particular bit got you out of a jam.
Disagree With Our Choices?
That’s okay! We know personal preferences take a front seat in determining the best drill bit, and every Pro is different. Do Pro Tool Nation a favor and tell us what your top pick is and why you love it. Feel free to put it in the comments below or on Facebook, Instagram, and Twitter!
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