We've given our opinion on the best drills overall — covering wood, metal, concrete, and more. In this go-around, we wanted to identify the best drill for metal applications. This includes hardened steel, stainless steel, aluminum and more. We even wanted to see which bit would do a good job of drilling hardened bolts like you'd find in an engine block. People also ask us about drill bits that drill through rebar. These are the parts we turn to and should lead you in the right direction.
Obviously, the best drills for hardening metal or steel contain a cobalt mixture. These cobalt bits use an alloy containing 5%–8% cobalt. This cobalt forms part of the steel mix so the hardness of the drill does not wear away with coatings such as titanium drills. It runs through the whole bit.
You can also sharpen these bits – another huge plus. This is important once you realize that cobalt drills cost much more than other types of twist drills. Unlike black oxide or titanium bits, you'll want to keep these bits on hand for emergencies.
When drilling with a cobalt bit, put a drop of oil on the metal to keep the cutting edge cool as it cuts. You'll also want to consider placing some wood underneath the steel if possible. This allows you to cut through the material cleanly without striking the underlying surface which could dull the cutting edge.
What does hardened steel mean?
When we talk about drilling in hardened steel, we are referring to medium or high carbon steels that are usually made using a heat treating and tempering process. Hardened steel is durable enough to resist abrasion, corrosion, and abrasion. Most of the steel we see in mechanical engineering, energy production and transportation is basically hardened steel. The best metal drills can be designed specifically for these hardened steel applications or optimized for speed on softer carbon steels.
Stainless steel
Stainless steel is an alloy steel containing at least 10.5% chromium, available in different grades. Due to its resistance to rust and stains, good sheen and low maintenance, it has many commercial uses including cookware, tableware, appliances, construction fasteners and surgical instruments.
However, regardless of any differences in appearance or chemical composition, hardened steel and stainless steel are difficult to drill into. Using a drill press is often the best way to get high-quality results.
Our best hardened steel drill bits include:
Best Drill Bits for Hardened Steel
Drill America D/A29J-CO-PC 29-Pack Cobalt Set
The M42 cobalt bits from Drill America drilled well through anything we threw at them. After testing multiple materials, we have selected their jobber bits as our best hardened steel bits.
These bits have the expected 135° split point which gives you a good, consistent and efficient drilling speed. jobber length drill bits are very effective in cordless drills for field drilling. They are manufactured in accordance with National Aerospace Standard 907. Due to their hardness, you can drill holes up to 30% faster than with conventional M2 HSS drill bits. Drill America also doesn't grind out the shafts on their larger drills – so you get more rigidity, but you still need a 1/2" chuck to drive them.
Use these bits when drilling into hard, high tensile materials such as stainless steel or even titanium. We chose the D/A29J-CO-PC kit. It contains 29 bits in a shatterproof casing. The round housing allows you to easily remove the bits you need.
Get the Jobber Length Drill America D/A29J-CO-PC kit for just $113.
Also consider:
DeWalt 29 pieces. Industrial Cobalt Pilot Point Bit Set
We love the pilot point tip and convenient case that come with these DeWalt Cobalt metal bits. They do a good job on steel and maintain a sharp edge after drilling a lot of holes.
The 29-piece set sells for about $110.
Irwin 29-Pack Cobalt M-42 Metal Index Bit Set
If you plan on drilling in hardened metal or steel, we like the Irwin 29-Piece M-42 Cobalt Drill Set as our best metal drill set. To be honest, our nod is not the fastest drill. This is related to the use of M42 high-speed steel and the excellent case.
Many less expensive cobalt bits use M35 steel with 5% cobalt. M42 steel uses an 8% cobalt mixture. This gives it greater hardness. It also allows you to drill at higher speeds than the M35. Irwin actually sells an M35 cobalt kit if you're not going to drill in hardened steel.
Which brings us to this case. If you do a lot of drilling – your drill bits matter. Visiting bits can be frustrating ( we 're talking Milwaukee!) or very successful—like this Irwin 3-tier swing box. We love the easy access to the bits, and you can easily tell the size from the front of each bit. Overall, this $152 kit gives you the best bit for a variety of metal applications.
Not bad:
Irwin 29-Pack Cobalt M-35 Metal Index Bit Set
The Irwin 29-Pack Cobalt M-42 Metal Index Bit Set performs very similarly to the M42 set. There is less cobalt in the steel mixture, it just heats up a little faster. You get the same big case. The tradeoff is cost. You can get this set for just $130.
Best Stainless Steel Drill Bits
For anyone looking for the best stainless steel drill bits, we have good news. The bits you use on hardened steel will work on stainless steel as well. Hardened steel is a high carbon steel medium that has been heat treated, quenched and finally tempered. Stainless steel alloys contain chromium (at least 10%) and nickel, making them corrosion resistant. As a mild steel, stainless steel has a natural hardness and does not require conventional hardening.
Drilling stainless steel requires a strong bit – the same M42 cobalt bit we recommend above. Having said that, stainless steel actually hardens when heated – so drilling slowly will often help you drill through the material more efficiently. Use cutting oil or a similar lubricant when drilling in stainless steel and apply sufficient pressure for steady material removal. Even the best stainless steel bits heat up over time, so be prepared to monitor for heat buildup.
Best Steel Drill Bits (Non-Hardened Carbon Steel)
Milwaukee Red Helix Cobalt Bits
The Milwaukee Red Helix cobalt drill bits listed in our best drill bits article feature a variable flute design for quick debris removal. too fast? About 30% faster than most other 135° diverging bits we tested. Their unique design not only helps them drill efficiently, but also aids in cooling. The tradeoff is that the bits get thinner towards the tip. Milwaukee solved that by making them a little shorter than some others we've seen. However, they also extend the groove down to the shaft. The result is a more compact drill with similar drilling depths.
A 135° bifurcation point tip helps start drilling, and larger sizes feature chipbreakers – grooves at the midpoint of the cutting edge to further reduce heat buildup. We love how fast these bits drill and how well they remove steel in a tight, efficient helix. The unique combination of cutting head and flute design make them our best drills for steel – especially carbon steel.
Missing 1/4" hex bits, use them in your drill or drill press when you need to use them to work thicker, harder metals.
Thanks to the cobalt-steel blend, plan to sharpen the tips as they become dull from use. The value of this kit makes them the best drill bits for steel.
You can find a 15-piece set for $27 or a 29-piece set for $110.
Also consider:
DeWalt Industrial Cobalt Pilot Point Bits
We love the build quality of the DeWalt Cobalt Pilot Bit Set. It has a tapered core that gradually increases the stiffness of the drill as it approaches the base. If you plan to cut stainless steel, give these bits a try – they won't disappoint and will make really clean holes in hardened steel.
The 29-piece set sells for about $110.
Best Rebar Drill Bits
Diablo Reinforced Demon Bit
Sometimes you need to drill through steel…but the steel is buried in concrete. For these applications you need something like the Diablo Rebar Demon SDS-Max and SDS-Plus bits. We like this design better than the Bosch rebar cutter because you use the same bit to drill and penetrate the rebar. With the Bosch, you can drill in hammer mode, switch to the rebar cutter in rotary-only mode, and then go back to the original bit to finish the hole.
These bits quickly drill through the concrete and then continue through the rebar. At this point, you really won't find anything else competing on the market, so it's an easy recommendation for productivity. We believe in accessories that power your work – so if something simple saves you time and money, that's a huge win for us. Pricing ranges from $6 to $217.
Also consider:
SDS-Max bit for Bosch rebar cutting machine
As we mentioned above, Bosch rebar cutting bits offer a viable option, but they will slow you down while doing the job. These bits should last a long time since they only cut rebar metal, but we generally prefer a single cutting solution. Buy Bosch rebar cutters here.
Milwaukee Hole Dozer Carbide Hole Saw
Milwaukee dozers with carbide teeth really win when it comes to metal drilling. It can handle stainless steel, and certainly anything softer or milder than stainless steel. These are some of the best hole saws for metal drilling that electricians, HVAC and/or MRO professionals can use.
Because they work so effectively on both metal and wood, any professional looking for a set of all-purpose hole saws should quickly fall in love with their productivity. It outperforms bi-metal blades by a wide margin and handles materials that a carbide hole saw can't (or shouldn't) touch. You can buy kits for $105-190
Irwin Unibit Cobalt Step Bits
Our team uses Irwin Unibit Cobalt step drill bits for any quick thin metal drilling application. A cobalt blend gives these bits a longer life. Since step bits are expensive and extremely difficult to sharpen, we want them to be as durable as possible.
Irwin provides Speedpoint hints for these bits. It helps start the hole quickly and reduces drift. We also have to admit that these became our best metal step bits, partly because Irwin laser etched the measurements on the inside of the flute. They don't wear out as quickly as other bits we've used.
Get a 3-pack for $69
Also consider:
Milwaukee pace
Several step drill bits offer a viable solution for electricians and others looking to drill through sheet metal and thicker materials. While we love the Irwin Cobalt model above, the dual-flute Milwaukee step drill is conveniently configured for common job site needs. You can buy these titanium aluminum nitride coated bits in various kits from $100 to $210.
diablo step
Diablo stepper bits promise to cut twice as fast and last 6 times longer. They attribute this in part to the precision CNC grinding process. We like the 132° split point tip, which requires little to no pre-drilling. You can get them in sizes 1/2 to 1-3/8 inches. Prices range from $29 to $65 per bit.
Titanium (coated)
Drills made with a titanium nitride coating resist corrosion and friction. It beats black oxide because it increases surface hardness and is better at reducing heat when drilling through metal. We absolutely keep these as a minimum for metal drilling.
With titanium nitride, you have to remember that it will only cover the drill bit. As the coating wears off the cutting edge, you pretty much have to replace them. Do not use these bits for drilling in hardened steel or stainless steel – if you expect them to last, then do not use these bits.
M35 and M42 cobalt (steel mix)
Our best cobalt drill bits for metal drilling are made from an alloy (M42) containing 8% cobalt. You can also find these bits with a 5% cobalt mix (M35). Since the cobalt is mixed into the steel, it won't wear down like titanium or black oxide coatings. It also means you can sharpen them with something like the Drill Doctor 750X Drill Bit Sharpener before replacing them. This helps save money when you buy these more expensive drill sets.
Cobalt bits are our go-to for drilling through metals – especially hardened steel and stainless steel.
We may have missed something along the way – we get it. At some point, we have to draw the line and finish the article. With that being said, let us know what you think is the best metal drill bit. Leave a comment below – especially if you have a "heroic" story about how a particular detail got you out of trouble.
Disagree with our selection?
It doesn't matter! We know that personal preference comes first in determining the best drill, and every Pro is different. Do Pro Tool Nation a favor and tell us what your top picks are and why you like them. Feel free to drop it in the comments below or on Facebook, Instagram and Twitter!
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