Specs are compiled from manufacturer listings and verified buyer reviews and can change over time — please confirm the key details on the product page before buying.
Drilling into hardened steel without the right bit is a recipe for broken bits, wasted time, and ugly holes. You need a bit made from cobalt or carbide — plain high-speed steel just gets chewed up. This guide walks through seven sets that actually handle the job, from single heavy-duty bits to full kits.
I’m Mohammad Maruf — the founder and writer behind Gardening Beyond. 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.
You need bits that can handle the heat and hardness of tough metals without dulling mid-hole, so here is a close look at the best drill bits for hardened steel for different budgets and job sizes.
Quick Picks
- Pro Edge M35 Cobalt Drill Bit Set Titanium Aluminum Nitride — Best Overall
- toolant Cobalt Drill Bit Set for Metal and Steel — Pro Grade Pick
- Irwin Tools IRWIN Drill Bit Set — Brand Trusted
- Yougfin Cobalt Drill Bit Set 21PCS M35 1/16″-3/8″ — Budget But Capable
- WildBossy M35 Cobalt Drill Bit Set 20PCS — Versatile Kit
- Narwhal 1/2 Inch Cobalt Drill Bits — Heavy Single-Size
- Sinyeenglon 5/8 Drill Bit for Metal and Hardened Steel — Oversize Specialist
How To Choose The Best Drill Bits for Hardened Steel
Choosing a bit for hardened steel is not the same as grabbing a general-purpose set. You need the right material, point geometry, and coating to survive the friction and hardness of tough alloys. Here is what actually matters.
Cobalt content separates the contenders from the casualties
Bits made from M35 cobalt steel contain 5% cobalt mixed into the high-speed steel. That extra alloy boosts the material’s red hardness — it stays hard even when the tip glows from friction. Plain HSS bits soften fast on hardened steel and lose their edge, while a cobalt bit keeps cutting. The data shows bits with M35 material and a rating up to 67 Rockwell hardness, which cuts faster and lasts longer on tough jobs.
Point angle and coating determine how it starts and survives
A 135° split point is the standard for hardened steel because it bites into the surface without needing a center punch first — it reduces walking and keeps the hole where you aimed it. Coatings like Titanium Aluminum Nitride (TiAlN) add a layer that handles high temperatures and oxidation, so the bit does not wear down as fast. Some bits skip the coating and rely on the bare cobalt alloy, which also works fine with proper lubrication.
Shank style and case quality matter more than you think
A tri-flat shank (three flat sides on the round shaft) gives the chuck a better grip than a round shank, which matters when drilling hard materials that can twist the bit. A storage case keeps bits organized and protects the sharp edges — some cases are sturdy plastic with engraved sizes, while others use stickers that can peel off. If you carry bits to job sites, look for a case that survives being tossed in a toolbox.
Quick Comparison
| Model | Best For | Material | Cutting Diameter | # of Pieces | Amazon |
|---|---|---|---|---|---|
| Pro Edge M35 Cobalt TiAlN 20pc | Premium all-around set | M35 Cobalt TiAlN | 1/16″-1/2″ | 20 | Amazon |
| toolant Cobalt Pro TiAlN 21pc | Pro-grade heavy drilling | M35 Cobalt TiAlN | 1/16″-1/2″ | 21 | Amazon |
| IRWIN Cobalt Alloy 15pc | Trusted brand for longevity | Cobalt Alloy Steel | — | 15 | Amazon |
| Yougfin Cobalt M35 21pc | Budget-friendly large set | M35 High Speed Steel | 1/16″-3/8″ | 21 | Amazon |
| WildBossy M35 Cobalt 20pc | Versatile jobber-length kit | M35 Cobalt Steel | 1/16″-1/2″ | 20 | Amazon |
| Narwhal 1/2″ Cobalt 3pk | Heavy single-size work | M35 Cobalt | 0.5 Inches | 3 | Amazon |
| Sinyeenglon 5/8″ M35 Reduced Shank | Single oversize hole | M35 Cobalt | 0.63 Inches | 1 | Amazon |
In‑Depth Reviews
1. Pro Edge M35 Cobalt Drill Bit Set Titanium Aluminum Nitride Coated (TiAlN) 20pc
A TiAlN-coated 20-piece set that pairs a bullet-point tip with serious heat resistance.
You get fewer bit changes because this set uses Titanium Aluminum Nitride (TiAlN — a coating that handles extreme heat) instead of basic titanium. The coating on these M35 cobalt bits reaches a hardness of 70HRC (Rockwell Hardness C-scale, a standard measure for tool hardness). So when you drill stainless steel roll pins or galvanized steel, the extra heat tolerance means you swap a dull bit less often.
Buyers report these are sharp, well-made bits that work excellently on galvanized steel, and one noted they are a bargain — a 10-pack for the price of two at the hardware store. The bullet point tip design helps center the bit so it does not wander on a smooth surface, and the double spiral flutes push chips out of both through-holes and blind holes. Compared to the toolant set below, this one uses a bullet point tip instead of a pilot point, meaning it is designed to self-center rather than follow a pre-drilled starter.
TiAlN edge: The coating adds real high-temp protection for repeated holes in hard metals without dulling fast.
Missing some duplicates: The 20-piece count includes 14 sizes, so you get extras only on the smallest bits — if you snap a 1/2″ bit, there is no backup in the case.
Grab this if: you want a premium coated cobalt set that will handle stainless and hardened steel all day without needing sharpening every few holes.
Not your pick if: you need multiple bits of the same size for production work — this set focuses on size coverage, not duplicates.
2. toolant Cobalt Drill Bit Set for Metal and Steel (Pro), TiAlN Coated, 21pc
Twenty-one cobalt bits with a TiAlN coating that bumps surface hardness to 89HRC.
This set punches up the coating game — the Titanium Aluminum Nitride layer pushes surface hardness to 89HRC, which is the highest coating hardness in this lineup. That means the cutting edge resists wear from the friction of hardened steel and stainless longer than a standard titanium coating. The set covers 21 pieces with duplicate smaller bits (1/16″, 5/64″, 3/32″, 7/64″, and 1/8″ each come with a spare), which is useful when you are drilling a row of holes and snap a small bit mid-job.
Owners mention these bits are among the best they have ever used, staying sharp after numerous holes — one owner drilled 60 holes of 5/16″ in a heavy-duty trailer from the 80s without any issues. The pilot point (the data lists it as a pilot point style, not a bullet point) helps center the bit on contact, so you do not need to center-punch every hole. toolant also stands behind the set with a 90-day warranty, and one reviewer noted that when a bit snapped, the company replaced it with several new bits instead of just one.
89HRC coating: This is a legitimate step up for heat resistance, so the bit stays sharp longer on demanding cuts.
Case could be sturdier: Some customers note the storage case is decent but not heavy-duty — fine for a shop drawer but maybe not for daily throwing into a truck bed.
Choose this for: heavy, repeated drilling in tough metals where you want a coating that really resists heat and a set that includes spare small bits.
Pass if: you only need an occasional hole in mild steel — the TiAlN coating is overkill for softer materials, and standard cobalt bits would be more budget-friendly.
3. Irwin Tools IRWIN Drill Bit Set, Cobalt Alloy Steel, 15-Piece (316015)
A 15-piece cobalt alloy set from a name that has been making cutting tools for decades.
Irwin is a known quantity in cutting tools, and this 15-piece set is a more focused collection than the 20-plus piece kits above — you get the sizes you need without duplicates. The bits are made from cobalt alloy steel with a 135° split point, and the redesigned tip is meant to promote longer life. The case has a clear lid so you see what is inside, and the cases are stackable if you own other Irwin sets.
Reviewers point out these bits go through 3/8″ sheet steel like butter when used with cutting fluid and a low speed, and they hold an edge much better than cheaper bits. One buyer mentioned they are the only type of bit to use for stainless — run them at low speed with plenty of cutting fluid and never use hammer mode. The set does not include a 1/2″ bit, which a few owners mention as a gap. But if you need a reliable 15-piece set from a brand with a long history, this is a compact, no-nonsense option.
Consistent quality: Irwin has been making these long enough that you know what you are getting — no surprises in hardness or finish.
No 1/2″ bit: If you regularly drill large holes, you will need to buy a 1/2″ cobalt bit separately.
Reach for this if: you trust established tool brands and want a compact, solid set that covers the most common sizes without extras.
Look elsewhere if: you need a 1/2″ bit or a larger variety of sizes in the same case.
4. Yougfin Cobalt Drill Bit Set 21PCS M35 1/16″-3/8″
A 21-piece M35 set that covers up to 3/8″ and comes in a practical index case.
This set offers the widest range of sizes in the budget tier — 21 different sizes from 1/16″ up to 3/8″, all made from M35 high-speed steel with cobalt. The gold oxide finish is not a high-tech coating, but it provides some corrosion resistance while the cobalt content does the real work of keeping the edge hard. The 135° split point reduces the pressure needed to start the hole, which means less skidding on smooth steel surfaces.
Shoppers say the bits are very sharp and work especially well on stainless steel, with one noting they are essential for a lot of steel construction work. The case is a nice index-style that keeps bits in labeled slots, though a couple of reviewers mention the case can start to break apart over time — so it is best for a shop drawer rather than a daily tossed toolbox. Compared to the WildBossy set below, this one tops out at 3/8″ instead of 1/2″, but it gives you more intermediate sizes for finer work.
Lots of sizes: 21 sizes between 1/16″ and 3/8″ means you have the right bit for almost any small-to-medium hole without needing an adapter.
Case durability: The index case is convenient but not built for abuse — treat it gently to keep bits organized.
Best for: the DIYer or hobbyist who needs a full range of M35 cobalt bits up to 3/8″ and wants to keep them organized on a shelf.
Skip if: you regularly need 1/2″ holes — this set stops at 3/8″, so you will need a separate larger bit.
5. WildBossy M35 Cobalt Drill Bit Set 20PCS (1/16″-1/2″) Jobber Length
A 20-piece M35 set that covers both small and large sizes, including a 1/2″ bit, at a moderate price.
This set hits a balance — it includes sizes from 1/16″ all the way up to 1/2″, with duplicate pieces on the smaller bits (1/16″ through 3/16″ each come with two). The bits are made from M35 cobalt steel with a titanium surface finish, and they feature a 135° split point and a 3-flat shank. At 15.2 ounces for the whole set, it is noticeably heavier than a single-bit option like the Sinyeenglon 5/8″ bit (which weighs 2.1 ounces), giving you a sense of the amount of steel in the case.
Buyers report the set drills thin stainless steel effectively, with one noting the non-slip two-flat shank and tough cut. Another reviewer mentioned the set works great for drilling out snapped-off taps and studs. The data shows the bits are rated for hardened materials, though some variability in quality pops up — a few users found some bits were dull fresh from the pack. Overall, for the price, it is a solid range of sizes from a brand that responds to issues.
Covers 1/2″: Unlike the Yougfin set, this one includes a 1/2″ bit, so you can handle larger holes without a second purchase.
Inconsistent QC: A minority of owners mention a few bits in the set were dull or snapped quickly, so check each bit before a critical job.
Pick this if: you want a single set that covers everything from tiny pilot holes to 1/2″ holes without buying extra bits.
Not ideal if: you need guaranteed top consistency from every single bit — you may get a dud in the batch.
6. Narwhal 1/2 Inch Cobalt Drill Bits (3 Pack – Industrial Grade M35 Cobalt)
Three identical 1/2″ M35 cobalt bits for when you need multiple spares of the same size.
This is not a variety set — it is three copies of a single 1/2″ bit, each with a 6″ total length and a 4″ flute length. The bits are uncoated M35 cobalt with a 135° split point, and each has a straight shank. But for 1/2″ holes, having three bits means you can keep drilling even if one dulls or snaps mid-project.
Customers note excellent performance in thin stainless steel — one owner drilled approximately 80 holes and the first bit was still sharp. Another reviewer noted the bits ate through cast iron like plastic, calling it the best bit they had bought in 45 years. The plastic storage case is sturdy and labeled. If you regularly drill 1/2″ holes in hardened steel or stainless, having three spares saves you from stopping mid-job to run to the store.
Three identical bits: Practical for production work where a single bit would dull or break before you finish all the holes.
Only one size: If you need a range of sizes, you will need to buy additional Narwhal packs for each diameter.
Grab for: repeat 1/2″ holes in tough metal where you want backup bits in the same case so work never stops.
Pass if: you need more than one size — a multi-size set delivers better value per drilled hole.
7. Sinyeenglon 5/8 Drill Bit for Metal and Hardened Steel, M35 Cobalt Reduced Shank
A single 5/8″ M35 cobalt bit with a reduced shank so it fits a standard 1/2″ chuck.
When you need a 5/8″ hole but your drill only accepts a 1/2″ chuck, this is the solution. The bit has a cutting diameter of 0.63 inches (compared to the Narwhal’s 0.5-inch bit), but the shank is machined down to a 1/2-inch tri-flat shape so it fits standard chucks. At 2.1 ounces, the WildBossy 20-piece set weighs 15.2 ounces, but that makes sense — this is a single bit, not a full set. The gold oxide finish adds a layer of heat resistance, and the 135° split point helps it start cleanly without wandering.
Reviewers point out these are sharp, durable bits that drill stainless steel well, and one noted surprise at the quality. The plastic storage case keeps the bit safe and labeled. The data says the bit is suited for stainless steel, cast iron, steel plate, titanium, and more. If you occasionally need a large hole in hardened steel, this single bit is cheaper than buying a whole set just for that one size.
Reduced shank built in: No need for a separate adapter or a big drill — this bit drops into any drill that takes 1/2″ chucks.
One bit only: If you need multiple sizes, you will buy several of these individually, which adds up fast.
Choose this for: the occasional 5/8″ hole in hardened steel when you do not want to invest in a whole set for one job.
Not your pick if: you drill large holes regularly — a multi-bit set with a 5/8″ option gives you more sizes for similar money.
Understanding the Specs
M35 Cobalt Steel
This is the material that gives a bit its ability to cut hard metals. M35 is high-speed steel with 5% cobalt added, which keeps the cutting edge hard even when friction heats it up. The data shows bits measuring up to 67 Rockwell hardness. Compared to plain HSS (high-speed steel), M35 lasts longer on hardened steel before needing sharpening or replacement.
TiAlN Coating (Titanium Aluminum Nitride)
This is a coating applied to the bit surface that makes it more heat-resistant and harder than a standard titanium coating. The data shows TiAlN can push surface hardness to 89HRC on bits that use it. For drilling hardened steel, this means the coating slows down edge wear and lets the bit cut longer before dulling.
135° Split Point
This is the shape ground into the tip of the bit. A 135° angle is wider than the standard 118° point, and the “split” means there is a notch ground into the tip. This design allows the bit to bite into the steel without walking — it starts the hole exactly where you place it, so you do not need to drill a pilot hole or center-punch first. It also reduces the downward pressure required.
Reduced Shank
Some large-diameter bits have their shank (the part that goes into the drill chuck) machined down to a smaller size than the cutting diameter. For example, a 5/8″ bit with a 1/2″ reduced shank fits into a standard drill chuck, even though the cutting end is wider than the chuck can normally accept. This lets you drill larger holes without buying a heavy-duty drill with a bigger chuck.
FAQ
Can M35 cobalt bits drill through hardened steel?
What is the difference between a 118° and a 135° split point?
Do I need a pilot hole for cobalt drill bits?
How do I keep cobalt bits from breaking?
What size drill bit set should I buy for home use?
Can I use a cordless drill for hardened steel with these bits?
Are TiAlN coated bits worth the extra cost?
How long does a cobalt drill bit last?
Can I sharpen cobalt drill bits?
What does a reduced shank drill bit mean?
Final Thoughts: The Verdict
For most people, the drill bits for hardened steel winner is the Pro Edge M35 Cobalt TiAlN 20-piece set because it combines a heat-resistant TiAlN coating, a bullet-point tip for accuracy, and solid size coverage from 1/16″ to 1/2″ at a reasonable price. If you want a pro-grade coating with the highest surface hardness and spare small bits, grab the toolant Cobalt Pro TiAlN 21-piece set. And for a single big hole without buying a full set, the Sinyeenglon 5/8″ M35 reduced shank bit fits any standard chuck and handles the job.
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.
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