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Trying to drill into hardened steel, stainless steel, or cast iron with a standard bit is a frustrating experience. The bit skates across the surface, dulls quickly, and often snaps — leaving you stuck with a half-finished hole. Cobalt drill bits solve that by staying hard and sharp enough to chew through tough metal without smoking your drill or your patience.
I’m Mohammad Maruf — the founder and writer behind WellFizz. 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.
We have broken down the six best sets of cobalt drill bits on the market today, from bulk value packs to professional-grade kits, so you know exactly which one matches the metal you need to cut.
Quick Picks
- HIDOTOL 115PCS Cobalt Drill Bit Set M35 HSS — Best Overall
- Irwin Tools IRWIN 15-Piece Cobalt Alloy Steel Drill Bit Set (316015) — Pro Pick
- CaRoller 29-Piece M35 Cobalt Steel Drill Bit Set — Portable Workshop
- Mudder 80-Piece 1/8″ M35 Cobalt Drill Bit Set — Bulk Value
- BECOLLO 20-Piece 1/8″ Cobalt Drill Bit Set — Entry-Level
- RCINDUS 20-Piece 1/8″ M35 Cobalt Drill Bit Set — Budget Starter
How To Choose The Best Cobalt Drill Bits
Buying a set of cobalt drill bits is a straightforward decision once you know what the specs actually mean for drilling metal. These three factors matter most.
Cobalt Content and Steel Grade
Real cobalt bits use M35 high-speed steel with 5% cobalt. That cobalt additive keeps the cutting edge hard even when friction heats the bit to temperatures that would soften standard HSS. If a set does not say “M35” or “5% cobalt,” it is not the real thing for hardened steel work.
Point Style — 135° Split Point
Standard bits have a 118-degree point that tends to “walk” or skate across a smooth metal surface. A 135-degree split point has a chisel edge that bites into the material immediately, self-centers the hole, and reduces the pressure you need to apply. Every set in this guide uses a 135-degree split point — that is the right spec for metal.
Size Range and Piece Count
Fractional sets (1/16-inch to 1/2-inch) cover most home and shop drilling needs. Larger sets add letter sizes (A to Z) and numbered wire gauges (#1 to #60) for precision work like tapping holes or automotive repairs. More pieces mean you have the exact size ready without stepping up from a smaller bit, which strains the bit and the material.
Quick Comparison
| Model | Best For | Material | Number of Pieces | Cutting Diameter | Amazon |
|---|---|---|---|---|---|
| HIDOTOL 115PCS | Maximum size coverage | M35 Cobalt (5%) | 115 | — | Amazon |
| IRWIN 316015 | Professional brand reliability | Cobalt Alloy Steel | 15 | — | Amazon |
| CaRoller 29-Piece | Portable pro set | M35 Cobalt Steel | 29 | 1/16″ to 1/2″ | Amazon |
| Mudder 80-Piece | High-volume shop supply | M35 High Speed Steel | 80 | 0.13 Inches | Amazon |
| BECOLLO 20-Piece | Entry-level value | Cobalt Steel | 20 | 0.13 Inches | Amazon |
| RCINDUS 20-Piece | Budget starter pack | M35 Cobalt | 20 | 0.13 Inches | Amazon |
In‑Depth Reviews
1. HIDOTOL 115PCS Cobalt Drill Bit Set M35 HSS
One indexed metal case holds the size you need every time.
This set gives you 115 pieces, including 26 letter sizes from A to Z and 60 numbered wire gauges from #1 to #60. Compared with the IRWIN’s 15-piece set, you get 115 bits versus 15. The M35 high-speed steel with 5% cobalt lets you drill into hardened metals such as stainless steel, cast iron, and titanium alloy without the edge collapsing.
Buyers report these bits are “very sharp and durable” and that one owner “drilled through harder material than my regular drills could.” The 135-degree split point self-centers on the workpiece so you do not have to fight walking on a smooth surface, and the fully ground twist design clears chips faster while reducing friction heat. The metal case with an indexed holder keeps every bit in its labeled slot — no more digging through a loose pile for the right gauge.
Compared to the CaRoller set, the HIDOTOL holds 115 pieces versus 29, making it the obvious pick if you need letter and wire sizes for precision or automotive work. The trade-off is weight: at 7.5 pounds, this case is a bench kit rather than something you clip to a tool belt like the CaRoller’s cup-style holder.
Size coverage you can count on
- Three size systems (fractional, letter, wire) in one case — 115 bits total
- M35 cobalt stays hard through high-temperature drilling into stainless and titanium
- 135-degree split point prevents walking; buyers confirm bits are sharp from the start
One real consideration
- Heavier than portable cases; 7.5 pounds stays on the bench, not on a belt
Best for precision and variety: If you drill into hardened metals regularly and want every fractional, letter, and wire size in an organized metal case, this is the set that makes sure you never reach for the wrong bit.
Trade-off: The weight and case size make this a stationary shop kit rather than a pouch you carry up a ladder.
2. Irwin Tools IRWIN 15-Piece Cobalt Alloy Steel Drill Bit Set (316015)
Jobsite-tested brand with a shank that locks tight in modern chucks.
IRWIN built this 15-piece set around a three-flatted shank design, meaning the shank has three flat sides instead of a perfectly round shaft. That shape gives your keyless chuck three flat surfaces to grip, so the bit does not spin or slip when you are leaning into a tough piece of stainless steel. Each bit is made from cobalt alloy steel with a 135-degree split point that centers on contact, eliminating the skating you get from cheaper 118-degree tips.
The set comes in a clear-lid case that stacks with other IRWIN cases, so you can snap together a custom kit for different jobs. At 11.2 ounces, the whole set is light enough to toss into a toolbag without thinking about it. Keep in mind that 15 pieces is a fraction of the size range you get from a 115-piece set like the HIDOTOL — you will have fractional sizes but no letter or wire gauge bits, which limits precision work.
If you already own a big kit on the bench and need a portable set that stays tight in a keyless chuck on a jobsite, the IRWIN three-flatted shank is exactly what you want. For metalworking pros, the smaller selection means you will still reach for the indexed case on complex jobs.
Shank design stands out: The three-flatted shank prevents spin-out in keyless chucks — a real-world advantage over round-shank bits when drilling overhead or in tight spaces.
Size limitation: Fifteen fractional bits cover the common sizes, but you will not find letter or wire gauges here. That is fine for general construction metal drilling, less so for precision machining.
Reach for this if: You work on job sites where your drill’s keyless chuck has to hold the bit securely under hard pressure, and you need a lightweight, stackable case.
Look elsewhere if: You need a broad size range including letter and wire gauges for automotive or close-tolerance work.
3. CaRoller 29-Piece M35 Cobalt Steel Drill Bit Set
A 29-piece range in a cup that clips to your belt and stays close.
The CaRoller set covers fractional sizes from 1/16-inch up to 1/2-inch across 29 pieces, versus 15 pieces in the IRWIN set, but with a completely different carrying philosophy. Instead of a flat case, it comes in a cup-type round holder with a built-in clip that attaches to your tool belt. That means every bit is within reach while you are on a ladder or moving between workstations — no setting the case down, opening it, and picking it back up.
The bits are made from M35 cobalt steel with a 135-degree split point, so they self-center in stainless steel, cast iron, and titanium alloy. The amber coating adds wear resistance, and the fully ground twist design reduces friction for cooler drilling. Compared to the HIDOTOL, the CaRoller has 29 pieces versus 115, so you get a solid selection of fractional sizes but no letter or wire gauge bits. The cup holder keeps everything organized but takes up less bench space than the 7.5-pound metal case.
For woodworkers and handymen who move around a shop or a construction site, the CaRoller trades maximum piece count for instant accessibility. If you work from a single bench all day, a flat indexed case may suit you better.
Belt-clip advantage: The cup-type holder clips to a tool belt, so bits stay with you instead of sitting on a bench. That is a genuine time-saver on multi-location jobs.
No letter or wire gauges: The 1/16-inch to 1/2-inch range covers common fractional holes, but if you frequently drill non-fractional sizes, you will need a second set.
Best for mobile work: If you move between a workbench, a ladder, and different job spots, the cup clip and 29-piece fractional range make this the most portable cobalt set on the list.
Caveat: Professionals who need full letter and wire gauge coverage will still need a larger bench kit.
4. Mudder 80-Piece 1/8″ M35 Cobalt Drill Bit Set
Eighty identical 1/8-inch bits for high-volume or replaceable-use drilling.
This Mudder set is different from every other option here because it gives you 80 bits of the same size — 1/8-inch — rather than a range of sizes. If your work consistently needs one diameter, or if you burn through small bits quickly on abrasive materials like cast iron and titanium alloy, having 80 identical bits on hand means you never stop to resharpen. Each bit is M35 high-speed steel with 5% cobalt, 135-degree split point, and a 2-flute spiral design that clears chips.
The bits measure 0.13 inches in cutting diameter, with diameter accuracy controlled within -0.03mm. The 135-degree split point prevents walking on hard surfaces, and the twist design helps clear chips faster. No other set in this guide offers 80 copies of the same cobalt bit — the HIDOTOL gives you 115 different sizes, not 80 of one size, so the Mudder serves a very specific purpose.
If you run a fabrication shop where 1/8-inch holes are the standard, or you break a lot of small bits drilling hardened metal, the Mudder 80-pack keeps you drilling without interruptions. If you need multiple hole sizes, skip this and choose the HIDOTOL or CaRoller.
Built for volume
- Eighty identical bits mean you never stop to sharpen or hunt for the right size
- M35 cobalt handles hardened metals including stainless steel and titanium alloy
- Diameter accuracy within -0.03mm for consistent hole fit
Single-size limitation
- All 80 bits are 1/8-inch — you get no other diameters
Perfect for high-use situations: If your work revolves around a single 1/8-inch hole size in hardened metal, this bulk pack saves you from frequent replacement trips.
Not for variety work: Anyone who needs multiple diameters for different projects will need a second set alongside this one.
5. BECOLLO 20-Piece 1/8″ Cobalt Drill Bit Set
A straightforward 20-pack of 1/8-inch cobalt bits without extra frills.
If you only need a handful of 1/8-inch cobalt bits for occasional drilling into stainless steel or cast iron, the BECOLLO set gives you 20 pieces made from cobalt steel with 5% cobalt content at a low entry cost. Each bit uses a 135-degree split point for self-centering and a fully ground surface that reduces friction for faster cutting. The bits are manufactured in accordance with ANSI B94-11M standards, so the dimensions are consistent with industry specs.
Like the RCINDUS set below, the BECOLLO comes in a plastic case for storage, and at 0.1 kilograms (about 3.5 ounces) it is light enough to toss in any drawer or tool pouch. The 0.13-inch cutting diameter is the same as the Mudder bits, but you get 20 pieces instead of 80. Compared to the HIDOTOL or CaRoller, you do not get any size variety — all bits are 1/8-inch — which keeps the price low but limits what you can drill.
This is a fine starter pack for a homeowner who needs to drill into a stainless steel appliance or cast iron bracket once in a while. For regular metalwork, the extra investment in the CaRoller 29-piece or HIDOTOL 115-piece gives you the range and density to handle unexpected hole sizes.
Low-cost way to try cobalt: Twenty bits at this price let you experience the difference cobalt makes in hardened steel without committing a lot of money.
Single-size limitation: All 20 bits are 1/8-inch. You will need separate bits for any other hole diameter.
Good for light occasional use: If you seldom drill into stainless or cast iron and want a small backup pack, this set gets the job done.
skip it if: You work on metal regularly and need multiple bit sizes — you will outgrow this set quickly.
6. RCINDUS 20-Piece 1/8″ M35 Cobalt Drill Bit Set
Factory-direct M35 material at a price that competes with basic HSS sets.
RCINDUS markets this 20-piece set as factory-direct M35 high-speed steel containing 5% cobalt — the same grade used in premium sets like the HIDOTOL. Each bit has a cutting diameter of 0.13 inches (3.175mm) with accuracy controlled within -0.03mm. The 135-degree split point provides automatic centering, which stops the bit from walking on a hard surface, and the full grinding and hardening processes give the cutting edge consistent geometry.
The set covers the same 1/8-inch single size as the BECOLLO pack and the Mudder 80-pack, so you get no diameter variety. At 20 pieces, it replaces dull or broken bits at a low per-bit cost. Compared to the HIDOTOL’s 115-piece range, the RCINDUS is a narrow tool for a single-size job. But if all you need is a handful of 1/8-inch cobalt bits to get through a stainless steel pipe or a cast iron block, this set gets you into M35 material without the premium markup.
The plastic storage case keeps the bits organized on a shelf, and the 135-degree split point means you will not fight skating on the first hole. For anyone who already owns a fractional set but needs a backup supply of the most commonly used 1/8-inch size, this is the most affordable way to keep going.
Factory-direct value
- M35 steel with 5% cobalt at a budget price point
- Diameter accuracy controlled within -0.03mm for consistent holes
- 20 bits provide a comfortable backup supply
Single-size limitation
- All 20 pieces are 1/8-inch — no size range for varied projects
Ideal for backup or single-size work: If you already have a general set but burn through 1/8-inch bits on hardened metal, this pack gives you M35 quality at the lowest per-bit cost.
Not a primary set: If you have no other cobalt bits and need multiple diameters, you will be limited by the single 1/8-inch size.
Understanding the Specs
M35 Cobalt Steel (5% Cobalt)
M35 is a specific grade of high-speed steel that includes 5% cobalt in the alloy. The cobalt adds hot hardness — the bit stays hard even when friction raises the temperature beyond what regular HSS can tolerate. That is the difference between drilling through stainless steel slowly and having the bit edge soften mid-hole. If a set does not specify “M35” or “5% cobalt,” it is not the real thing for hardened metal work.
135-Degree Split Point
Standard drill bits have a 118-degree point that tends to skate or “walk” across a smooth steel surface as you start drilling. A 135-degree split point adds a chisel-edge notch at the tip that bites into the metal immediately. This self-centers the bit so you do not have to center-punch every hole, and it reduces the downward force you need to push through tough material. Every set on this list uses a 135-degree split point — it is the defining feature of a real metal-drilling cobalt bit.
FAQ
What is the difference between cobalt drill bits and titanium drill bits?
Can I use cobalt drill bits on wood or plastic?
How do I know if a set uses real M35 cobalt steel?
Why does the 135-degree split point matter?
What speed and pressure should I use with cobalt bits?
Will cobalt bits fit all drills?
How long does a cobalt drill bit last?
Do I need cutting fluid with cobalt bits?
What sizes do cobalt bit sets typically cover?
How do I sharpen a dull cobalt drill bit?
Final Thoughts: The Verdict
For the majority of shoppers, the best cobalt drill bits winner is the HIDOTOL 115-Piece Set because its indexed metal case delivers every fractional, letter, and wire gauge size you need for hardened-metal work. If you want a portable set that clips to your belt and covers the essential fractional range, grab the CaRoller 29-Piece Set. And for a reliable jobsite option with a shank that stays locked in keyless chucks, the IRWIN 15-Piece Set is the one to pick if you need a shank that won’t slip in a keyless chuck.
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.
As an Amazon Associate, WellFizz earns from qualifying purchases. This does not affect which products we feature.
Mo Maruf
I created WellFizz to bridge the gap between vague wellness advice and actionable solutions. My mission is simple: to decode the research and give you practical tools you can actually use.
Beyond the data, I am a passionate traveler. I believe that stepping away from the screen to explore new environments is essential for mental clarity and physical vitality.