Our Top Picks
- 135-degree split point tip
- Self-centering
- Gold oxide coating
- For heavy-duty use
- 135-degree tip
- Includes professional carry-case
- Engineered for professionals
- Split-point tip
- M42 grade
- Pilot point design
- No need for pilot holes
- M35 grade
- 13-piece set
- 135-degree split point
- M35 grade
Our Review Criteria: Alloy grade comes before everything else in a cobalt bit: M35 carries 5 percent cobalt and M42 carries 8, and that difference sets both red-hardness and brittleness. We compared tip geometry next, favoring 135-degree split points and pilot-point starts that stop a bit from walking on smooth steel, then the usable fractional size range, shank type and chuck fit, and the case that protects the edges between jobs. Manufacturer specifications were cross-checked against patterns in real owner reviews, and each set’s drawbacks were recorded alongside its strengths. We confirm every pick is currently in stock and swap out anything that has been discontinued.
Standard high-speed steel bits give up fast in hardened steel or cast iron. They smoke, lose their edge, and snap. The best cobalt drill bits solve that, because the cobalt is alloyed through the whole bit, so they keep cutting at temperatures that would ruin a coated bit.
Cobalt bits drill iron, stainless steel, and titanium without dulling on the first hole. The catch is that not all cobalt is equal. The grade (M35 vs M42) sets the heat tolerance, and the tip geometry decides whether the bit bites or wanders on a smooth surface.
We sorted the current market by material grade, tip design, usable size range, and value, then confirmed every pick is one you can still buy today. Below are five cobalt sets worth owning, from a professional fractional index to a budget kit for the occasional hard-metal job.
What Is a Cobalt Drill Bit?
Cobalt drill bits are not just coated in metal. They are made from a solid steel alloy that contains a specific percentage of cobalt throughout the entire bit. Manufacturers grade these bits as either M35 or M42 based on the concentration of cobalt. M35 contains 5% cobalt, while M42 holds 8%.
The real advantage of cobalt is heat resistance. Drilling hard metal like stainless steel generates the friction heat that kills a standard bit by softening its edge. Cobalt holds its hardness far longer (a property called red hardness): M35 stays hard to roughly 1,050 F and M42 to about 1,150 F, which is why a cobalt bit keeps cutting where plain HSS would dull on the first hole.
However, there is a trade-off. Cobalt makes the bit harder but also more brittle. These bits can snap if you apply uneven pressure or let the drill walk. Shorter bits tend to be more durable because they flex less than longer ones.
Types of Cobalt Drill Bits
The alloy stays the same, but the shape decides the job. These are the four types you will run into:
Twist Bit
Twist bits are the standard image of a drill bit. They feature a cylindrical shaft with helical flutes to remove debris. This is the most versatile type of cobalt bit. You will use these for 90% of your metal drilling tasks. Look for split-point tips, which prevent walking on smooth surfaces.
Step Bit
Step bits look like a cone with stair-stepped ridges. A single bit can drill holes of various diameters depending on how deep you push it. These are excellent for drilling clean holes in thin sheet metal. They eliminate the need to change bits constantly when you need different hole sizes.
Countersink
Countersink bits create a conical hole that allows the head of a screw to sit flush with or below the surface of the material. While more common in woodworking, cobalt countersinks are essential when you need to fasten screws into metal plates without the heads sticking out.
Counterbore
Counterbore bits create a flat-bottomed hole. This allows a fastener with a flat underside, like a socket head cap screw, to sit flush. You will typically see these used in machinery assembly or automotive work where flush mounting is critical for moving parts.
How to Choose the Best Cobalt Drill Bit
Selecting the right set involves more than just picking a brand. You need to match the bit specifications to your specific project. Consider these factors before you buy:
Product Reviews
We sorted these picks by alloy grade, tip geometry, usable size range, and how they hold up in hard metal, then confirmed each one is still in stock. Whether you fabricate for a living or only reach for cobalt a few times a year, one of these sets fits.
Drill America 29-Piece M35 Cobalt Drill Bit Set
Best Cobalt Drill Bits For Hardened Steel
This 29-piece M35 set is aimed at machinists and serious DIYers who drill hard metal often enough to want a full fractional index. The 135-degree split point is the reason it cuts so cleanly: where a standard 118-degree tip skates on smooth steel and needs a center punch, this one bites on contact and starts a true hole without a pilot.
The 5% cobalt alloy does the real work, holding its edge in high-tensile steel and titanium where coated bits fade. The gold oxide finish adds a little lubricity to help chips clear. You get every fractional size from 1/16-inch to 1/2-inch in 1/64-inch steps, so this is the set to own if you need an exact-size hole rather than the nearest bit you happen to have.
The round shank seats firmly in any 3-jaw chuck. The plastic index case is the weak point and can crack if dropped, but the grind quality and consistency punch above what the kit costs, which is why it earns the hardened-steel pick.
Pros
- Tip Design: 135-degree split point prevents walking.
- Alloy: M35 cobalt steel resists high heat.
- Range: Comprehensive 29-piece size collection.
- Finish: Gold oxide aids chip flow.
Cons
- Price: Higher cost than standard steel sets.
- Case: The index case can be fragile.
Product Specs
| Number of pieces | 29 |
|---|---|
| Sizes (inches) | 0.063 to 0.50 |
| Tip | Split-point |
| Grade | M35 |
| Price | $$$ |
Irwin Tools M35 Cobalt Drill Bit Set
Best Heavy-Duty Cobalt Drill Bits
Irwin earns its place in pro toolboxes on grind quality, and this 29-piece set is the heavy-duty workhorse of the group. The M35 bits use a 135-degree split point that cuts feed pressure, so you do not have to lean on the drill to keep it biting, which matters when you are drilling abrasive metal all day and your wrist is the limiting factor.
You get the full fractional range from 1/16-inch to 1/2-inch. The standout is the metal index case: unlike the brittle plastic trays on most sets, it is rubber-lined, so the cutting edges are not chipping against each other every time the case rattles around in a truck. The downside is simply cost, this is one of the pricier sets here, but the symmetry of the grind and the alloy’s staying power make it the heavy-duty pick for anyone who drills metal for a living.
Pros
- Quality: Consistent grind and symmetry.
- Protection: Excellent rubber-lined metal case.
- Application: Reduced feed pressure required.
- Variety: Full 29-piece fractional set.
Cons
- Price: Expensive upfront investment.
Product Specs
| Number of pieces | 29 |
|---|---|
| Sizes (inches) | 0.063 to 0.50 |
| Tip | Split-point |
| Grade | M35 |
| Price | $$$ |
Bosch 14-Piece Cobalt Metal Drill Bit Set
Best Professional Cobalt Drill Bits
Bosch builds this 14-piece set from M42 (8% cobalt), the higher grade, so it tolerates more heat than the M35 sets here and holds up to continuous drilling in abrasive metal like cast iron and stainless. If you drill hole after hole in a production setting, that extra red-hardness is what keeps the edge alive longer.
A thick web stiffens the core to resist side-load snapping, and the three-flat shank stops the bit from spinning in the chuck under load. The split point starts accurately without a punch, and the 1/16-inch to 1/2-inch range covers the sizes most HVAC, electrical, and plumbing jobs call for. The catch with M42 is the same property that makes it cut: it is harder and therefore more brittle, so it punishes a tilted or wandering drill. Keep it square (a drill press is ideal) and it rewards you with the longest life of any set on this list.
Pros
- Grade: M42 alloy with 8% cobalt.
- Strength: Thick web design adds rigidity.
- Accuracy: No-skate split point tip.
- Durability: High heat resistance for production work.
Cons
- Brittleness: Can snap if the drill tilts.
- Cost: Premium pricing for M42 grade.
Product Specs
| Number of pieces | 14 |
|---|---|
| Sizes (inches) | 0.063 to 0.50 |
| Tip | Split-point |
| Grade | M42 |
| Price | $$ |
DeWALT Cobalt Pilot Point Drill Bit Set
Best Pilot-Point Cobalt Drill Bits
DeWALT’s Pilot Point geometry is what sets this 14-piece set apart. A small central tip starts the hole before the full diameter engages, so the bit drills a clean, round hole with little burring and no walking at startup, even on a slick stainless surface. If you mostly drill freehand without a punch, that is the feature that saves you ruined parts.
The M35 cobalt body handles the heat of stainless and angle iron, and the Pilot Point also reduces the grab-and-bind that happens when a bit punches through the back of thin metal. Sizes run 1/16-inch to 3/8-inch, which is the main thing to watch: the largest bit tops out at 3/8-inch, so for anything bigger you will need a separate large-diameter bit. For hand-drill work in the common sizes, though, it is one of the most forgiving sets here.
Pros
- Geometry: Pilot Point tip ensures clean starts.
- Ease of Use: Reduces bit walking significantly.
- Value: Good balance of price and performance.
- Storage: Tough case with rubber bumpers.
Cons
- Size Limit: Maxes out at 3/8-inch.
- Consistency: Smaller bits can be fragile.
Product Specs
| Number of pieces | 14 |
|---|---|
| Sizes (inches) | 0.063 to 0.375 |
| Tip | Pilot point |
| Grade | M35 |
| Price | $$ |
MACXCOIP M35 Cobalt Drill Bit Set
Best Budget Cobalt Drill Bit Set
If you only drill hardened steel now and then and cannot justify a pro-grade index, the MACXCOIP 13-piece set is the low-commitment way into real cobalt. It is the budget pick here, but it is genuine M35 cobalt rather than the coated HSS some bargain sets pass off as the same thing, so it cuts stainless, mild steel, and aluminum better than its price suggests.
The 135-degree split point self-centers and keeps the bit from walking on smooth metal, and the twist design clears chips well enough for the light-to-medium work this kit is meant for. The size range is the main limit: 13 fractional sizes from 1/16-inch to 1/4-inch, which covers pilot holes and small fasteners but stops short of large-diameter work. If you need anything past 1/4-inch, this is not your set.
Honest expectations matter at this price. These will not match the Irwin or Drill America bits for life span in continuous use, and the smaller bits can grab and leave a burr at the breakthrough point if you push too hard. Treat them as an occasional-use kit, run them slow with cutting oil, and they earn their keep in a home toolbox.
Pros
- Value: The cheapest way into genuine M35 cobalt.
- Material: Genuine M35 cobalt, not just coated HSS.
- Design: 135-degree split point self-centers and resists walking.
Cons
- Sizes: Limited range, maxes out at 1/4-inch.
- Finish: Smaller bits can grab and leave a burr at breakthrough.
- Case: The plastic index box feels flimsy.
Product Specs
| Number of pieces | 13 |
|---|---|
| Sizes (inches) | 0.063 to 0.25 |
| Tip | Split-point |
| Grade | M35 |
| Price | $ |
| Product | Best | No. of pieces | Sizes | Tip | Grade |
|---|---|---|---|---|---|
| Drill America M35 Cobalt Drill Bit Set | Hardened Steel | 29 | 0.063 to 0.50″ | Split-point | M35 |
| Irwin Tools M35 Cobalt Drill Bit Set | Heavy-Duty | 29 | 0.063 to 0.50″ | Split-point | M35 |
| Bosch Cobalt Metal Drill Bit Set | Professional | 14 | 0.063 to 0.50″ | Split-point | M42 |
| DeWALT Cobalt Pilot Point Drill Bit Set | Pilot-Point | 14 | 0.063 to 0.375″ | Pilot point | M35 |
| MACXCOIP M35 Cobalt Drill Bit Set | Budget Pick | 13 | 0.063 to 0.25″ | Split-point | M35 |
