As an Amazon Associate I earn from qualifying purchases. Picks are based on manufacturer specs, independent reviews and owner reports.
Our top picks
Short on time? Our top recommendation is the Irw in Cobalt Drill Bit Set 29-Piece.
Compare
At a glance
The traits that separate these picks, side by side.
In depth
The 10 best, explained
Why each made the cut, where it falls short, and who should buy it.
Best OverallIrwin
M42 cobalt with 8% cobalt content - highest cobalt grade for hardened steel
- M42 cobalt steel
- 8% cobalt content
- 135-degree split point
- 29-piece 1/16 to 1/2 inch
✓ Pros
- M42 cobalt with 8% cobalt content - highest cobalt grade for hardened steel
- 135-degree split point starts without a center punch on most surfaces
- Irw in is the benchmark bit brand used by professional machinists
- 29-piece coverage from 1/16 to 1/2 inch
✕ Cons
- Set price is high - individual bits available if only specific sizes are needed
Best Single BitIrwin
A single 1/4-inch cobalt drill bit from Irw in for drilling hardened steel, stainless and other tough metals.
- M42 cobalt
- 1/4 inch
- 135-degree split point
✓ Pros
- Cobalt steel holds its edge in hard metals
- Heat resistant for drilling stainless steel
- Buy only the size you need instead of a full set
- Widely available replacement size
✕ Cons
- Cobalt bits are brittle and can snap if side-loaded
- Needs low speed and cutting fluid for best life
- More expensive than standard HSS bits
Best DewaltDeWALT
Best DeWALT cobalt set. Its case rests on deWALT brand cobalt bit set at lower price than Irw in and included case with indexed storage for all 29 bits. One caveat, cobalt percentage not specified - likely M35 (5%) vs Irw in M42 (8%).
- Cobalt steel
- 29-piece
- 135-degree tip
- DeWALT case
✓ Pros
- DeWALT brand cobalt bit set at lower price than Irwin
- Included case with indexed storage for all 29 bits
- DeWALT quality consistent with their power tools
✕ Cons
- Cobalt percentage not specified - likely M35 (5%) vs Irw in M42 (8%)
Best BoschBosch
Bosch M42 cobalt at a lower price point than Irwin
- M42 cobalt
- 14-piece
- Bosch quality
✓ Pros
- Bosch M42 cobalt at a lower price point than Irwin
- 14-piece covers the most common drill sizes
- Bosch is a globally respected precision tool brand
✕ Cons
- 14-piece vs Irw in 29-piece - missing some sizes
Best DiabloDiablo
Diablo 18-piece at a lower price per bit for users who want cobalt capability without the Irw in premium. Its case rests on diablo has become a respected cutting tool brand and rated for hardened steel and stainless.
- Cobalt steel
- 18-piece
- Hardened steel rated
✓ Pros
- Diablo has become a respected cutting tool brand
- Rated for hardened steel and stainless
✕ Cons
- Less established reputation vs Irwin
Best CarbideKlot
Solid carbide is the only material that can drill heat-treated tool steel above 60 HRC
- Solid carbide
- For hardened steel over 60 HRC
- Slow speed drilling
✓ Pros
- Solid carbide is the only material that can drill heat-treated tool steel above 60 HRC
- Cobalt bits will not penetrate this hardness - carbide is required
- Used on broken bolt extraction when the bolt is case-hardened
✕ Cons
- Carbide is brittle - snap if drill wanders or catches
- Requires slow speed and constant cutting fluid - breaks easily without proper technique
Best UsaDrill America
Best USA-made cobalt bit. Its case rests on drill America is US manufactured - machinist community preference for domestic tooling and m42 cobalt specification. One caveat, higher per-bit price than import cobalt bits.
- USA manufactured
- M42 cobalt
- Machinist grade
✓ Pros
- Drill America is US manufactured - machinist community preference for domestic tooling
- M42 cobalt specification
✕ Cons
- Higher per-bit price than import cobalt bits
Best IndustrialNorseman
Best industrial cobalt bit. Its case rests on norseman is a professional machinist brand with decades of industrial use and longer service life than import cobalt in production machining. One caveat, specialty brand not available in retail stores.
- M42 cobalt
- Industrial grade
- USA made
✓ Pros
- Norseman is a professional machinist brand with decades of industrial use
- Longer service life than import cobalt in production machining
✕ Cons
- Specialty brand not available in retail stores
Milwaukee
Milwaukee brand consistency for Milwaukee drill users
- THUNDERBOLT cobalt
- Milwaukee quality
- 15-piece
✓ Pros
- Milwaukee brand consistency for Milwaukee drill users
- THUNDERBOLT cobalt rated for stainless and hardened steel
- 15-piece covers common sizes
✕ Cons
- 15-piece vs Irw in 29-piece coverage
Best Titanium AlternativeLenox
Titanium coating extends HSS bit life on mild steel and stainless
- Titanium nitride coating
- Multi-purpose
- Wood, metal, plastic
✓ Pros
- Titanium coating extends HSS bit life on mild steel and stainless
- General purpose for users who drill hardened steel occasionally
✕ Cons
- Titanium is a coating - when it wears through the bit becomes standard HSS
- Does not work on steel above 40 HRC - cobalt required
What to check before you buy
These are the factors that separate drill bits for hardened steel. Match them to how you'll actually use it before comparing prices.
- Battery platform: Major platforms each cover hundreds of tools. Choose one with the specialty tools you may need later.
- Brushless vs brushed: Brushless motors are more efficient and durable. Brushed tools are fine for occasional light use.
- Kits vs bare tools: Kits include batteries and a charger. Once you own batteries, bare tools are much cheaper.
- Voltage: 12V tools are compact for light work. 18V or 20V max tools handle most home projects. Higher-voltage platforms suit heavy cutting.
- Warranty: Check tool and battery warranty lengths and whether registration is required.
How we chose these picks
- We started from manufacturer specifications and feature lists, the verifiable foundation.
- We weighed reputable independent reviews from established tech and consumer publications.
- We read large volumes of verified-owner feedback to find patterns in reliability and satisfaction.
- We scored value: what you get for the price, not just absolute performance.
- We excluded products with thin — suspicious, or heavily incentivized review profiles.
We don't claim hands-on testing we haven't done. Assessments synthesize manufacturer specifications, reputable independent reviews and documented owner feedback. Read our methodology.
How to choose: the factors that matter
- Capacity and sizing — Measure your space and your actual use before falling for bigger-is-better. The right size is the one that fits your routine, not the spec sheet's maximum.
- Build quality and materials — Heavier-gauge materials, tight tolerances, and solid joints outlast thin, rattly construction. In reviews, look for longevity comments over first-impression praise.
- Ease of use and setup — Clear instructions, intuitive controls, and minimal assembly separate daily drivers from garage ornaments.
- Maintenance and cleaning — Whatever you buy will need cleaning. Removable, dishwasher-safe, or wipe-clean parts get maintained; fiddly ones get neglected.
- Warranty and support — A multi-year warranty signals the manufacturer expects it to last. Check what's actually covered, motors and frames matter more than accessories.
The bottom line
If you want the short answer: the top pick above suits most buyers, the value pick suits tight budgets, and the specialist picks suit specific needs. Match the pick to your use case, not to the hype.
FAQ
Common questions
What are the best drill bits for hardened steel 2026 right now?
Our top pick is the Irw in Cobalt Drill Bit Set 29-Piece (best overall), because m42 cobalt with 8% cobalt content - highest cobalt grade for hardened steel. The runner-up is the Irw in Cobalt Drill Bit Individual 1/4 Inch (best single bit), followed by the DeWALT DWA1269 Cobalt Drill Bit Set 29-Piece.
Which of the drill bits for hardened steel 2026 should I buy?
It depends on what matters most to you. For overall, choose the Irw in Cobalt Drill Bit Set 29-Piece. For single bit, choose the Irw in Cobalt Drill Bit Individual 1/4 Inch. For dewalt, choose the DeWALT DWA1269 Cobalt Drill Bit Set 29-Piece. For bosch, choose the Bosch CO14B Cobalt M42 Drill Bit Set 14-Piece.
Is the Irw in Cobalt Drill Bit Set 29-Piece worth it?
For most buyers, yes. It ranks #1 in our drill bits for hardened steel 2026 research, though set price is high - individual bits available if only specific sizes are needed.
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