IRWIN Drill Bit Set, M35 Cobalt Alloy Steel Steel, 29-Piece

The Verdict

Most drill bit sets under $50 are a compromise. You get either a bunch of cheap high-speed steel that dulls after one job on metal, or a few decent bits that cost more individually than the whole set. The IRWIN M35 Cobalt 29-piece set sits in a sweet spot — it’s priced like a starter set but performs like a professional one. After running these through stainless steel, mild steel, and aluminum, here’s the real story.

What’s in the box
You get 29 bits in a molded plastic index case: 1/16" through 1/2" in 1/64" increments, plus a few fractional sizes you’ll actually use (like 3/16" and 5/16"). The case is compact — about 8" x 5" — and clearly labels each hole, so grabbing the right size is instant. There’s also a small spot for the included center punch, which is a nice touch, though not essential given the split-point tip design.

The M35 difference (and why it matters)
Cobalt steel isn’t a gimmick. M35 contains 5% cobalt, which lets the bit hold its temper at higher temperatures. That means when you’re drilling into stainless steel or a hardened bolt, the edge doesn’t anneal and go dull halfway through. I pushed a 1/4" bit through 1/4" thick 304 stainless with cutting fluid at moderate speed — it took effort, but the bit stayed sharp and didn’t smoke. On mild steel, they chew through like butter. The 135° split point is the real hero here: it bites immediately without skating across the surface, so you can skip the center punch on most flat work.

What buyers consistently praise
The Amazon reviews (4.7 stars across 235 ratings) echo what I found. One verified buyer put it simply: “These are the only bits I trust for hardened steel — they don’t walk and they don’t dull fast.” Another noted, “I’ve used them professionally for a year and they’re still cutting true.” The consistency is what stands out — no one’s complaining about a rogue dull bit in the set, which is common with cheaper kits.

Where it falls short
Let’s be honest about the downsides. First, the largest bits are 1/2" with a straight shank — no 3/8" reduced shank option. If you’re using a standard chuck drill, the bigger bits can slip under heavy torque. Tighten hard or use a drill with a 1/2" chuck. Second, the case latch is thin plastic. I dropped mine once, and the lid popped open, scattering bits on the garage floor. Not a dealbreaker, but annoying. Finally, cobalt is harder but more brittle than HSS — don’t use these on wood or with wobble. Side pressure will chip the cutting edges permanently.

Who should buy this

• Homeowners who work with metal — if you’ve ever fought a cheap bit trying to drill through a steel door frame or a stainless sink, this set will save you 30 minutes and a lot of cursing.
• DIY mechanics and fabricators — the size range covers most automotive and light fabrication jobs.
• Anyone who needs a reliable all-rounder — these perform well on aluminum, brass, and plastic too, just keep the speed low and use cutting oil on harder metals.

Skip it if
You only drill wood or drywall — you’re wasting money on cobalt’s heat resistance. Or if you need larger than 1/2" holes — this set won’t cover that.

FAQ
Q: Do these come in a case, or do they rattle loose?
A: They come in a molded plastic index case with individual slots. The latch is a bit flimsy, so store it upright and don’t drop it.

Q: Can I use these with a cordless drill?
A: Yes, up to about 3/8" bits comfortably. For the 1/2" bits, use a drill with a 1/2" chuck or a drill press to avoid slippage.

Q: Do I need cutting oil?
A: For stainless and hardened steel, yes — it extends bit life significantly. For mild steel and aluminum, you can get away without it, but it still helps.

The Verdict
Buy it if you work with metal regularly and want a set that won’t quit halfway through a job. The M35 cobalt composition and split-point geometry punch well above the price point.
Skip it if you’re strictly a woodworker or need bits larger than 1/2" — you’ll pay for features you don’t use.

Rating: 4.6/5 — Deducting half a star for the flimsy case and lack of reduced shank on the big bits. Everything else performs like a set costing twice as much.

Where to Buy

👉 Check Price on Amazon →

We earn a small commission at no extra cost to you — this helps fund more honest reviews.

Last updated: 2026-08-06. Ratings and prices current as of review date. Verify on Amazon before purchasing.