Anyone who has burned through a standard bit trying to punch a hole in stainless steel knows the frustration. Regular high-speed steel softens at drilling temperatures, dulls fast, and leaves you with a half-finished hole. Cobalt alloyed drill steel changes that equation, holding its edge where lesser bits give up. This roundup covers five options spanning full assortments, single-size packs, and step designs, so whether you’re a fabricator running a mill all day or a weekend DIYer fixing a deck railing, there’s a fit here.
The Choices Worth Comparing
CaRoller Cobalt Drill Bit Set 29-Piece M35
STROTON Metric M42 8% Cobalt Drill Bits 2.0mm
TopLine No. 7 Cobalt M42 Drill Bits 4-Pk
SS SHOVAN M35 Cobalt Step Drill Bit Set 3PCS
Pro Edge Technology 13pcs Cobalt Jobber Drill Bit Set
The Details Behind The Selections
Twenty-nine sizes in one kit covers nearly every hole a home shop asks for, from pilot holes in sheet metal to larger bores in hardwood. The round shanks seat securely in standard three-jaw chucks, so nothing here demands special tooling.
Where the STROTON pack below goes deep on one metric size, this set spreads wide instead. That makes it the kind of purchase you make once and reach for across years of mixed projects, plumbing brackets to furniture assembly.
Notable Gains
- Broad 29-piece range means fewer mid-project trips to buy a missing diameter
- M35 cobalt-alloyed HSS resists heat buildup better than plain carbon steel bits
- Included cup-type holder keeps every size visible and sorted between jobs
- Suitable surfaces span steel, wood, plastic, and sheet metal
- Amber finish helps owners spot wear before a bit starts wandering
Things To Consider
- The holder takes drawer space, worth measuring your storage before ordering
- Cobalt bits are brittle compared to softer steel, so side loading can snap thin sizes
Who It Suits Best
Handymen and hobbyists who want one comprehensive kit rather than piecing together individual sizes over time.
Where A Sibling Pick Shines
Shoppers who mostly drill stainless in one specific diameter will get longer tool life from the STROTON Metric M42 8% Cobalt Drill Bits instead.
This is the purest M42 play in the lineup. Eight percent cobalt content pushes hardness into the 68 to 70 Rockwell C range, which is exactly what you want against work-hardening alloys like 304 stainless that chew up ordinary bits.
Each specification ships in its own packaging, a small detail that matters more than it sounds when you’re grabbing a 2.0mm bit from a crowded toolbox. Five identical pieces per pack also means a snapped tip doesn’t stall your afternoon.
What Works In Its Favor
- 68-70 HRC hardness holds cutting edges through repeated stainless jobs
- High cobalt content improves heat and wear resistance at speed
- Five-bit quantity supports production runs without constant reordering
- Individual per-size packaging keeps small diameters organized
Small Caveats
- One metric size only, so check your project’s hole spec before committing
- Extreme hardness makes these more snap-prone under lateral pressure than softer bits
Key Specs
Right Fit For
Fabricators and machinists cutting stainless, titanium, or hardened alloys on a regular schedule.
Reach For A Different Pick When
General household drilling across many materials fits the CaRoller 29-piece set far better than a single-diameter metric pack.
No. 7 lands at a 13/64 inch diameter, a common tap-drill size for 1/4-20 threads, which explains why tradespeople buy this pack in multiples. These are ground from solid blank rather than rolled, and ground flutes cut straighter and truer than rolled equivalents.
Compared with the STROTON’s metric sizing, this pack serves imperial threading work, the bread and butter of American fabrication shops. Four bits per order keeps a busy bench stocked through a season of stainless and titanium work.
The Case For It
- Ground-from-solid construction delivers cleaner, more concentric holes than rolled flutes
- 8% cobalt M42 steel targets high-tensile material without glazing
- Four-piece quantity suits shops that burn through this diameter regularly
- Jobber length balances reach with rigidity in handheld drills
Points To Note
- A single fractional size, so confirm No. 7 matches your tap chart first
- Bits this hard reward slow speeds and steady oil; forcing the cut shortens life noticeably
Whose Shelf It Belongs On
Professional welders and machine shops tapping 1/4-20 threads in stainless day after day.
Another Choice May Suit
Hobbyists wanting varied diameters for mixed repairs are better served by the Pro Edge Technology 13-piece jobber set.
A step drill works differently from a twist bit: each tier cuts a successively wider hole, letting one cone produce dozens of diameters. For electrical boxes, conduit knockouts, and automotive sheet panels, that replaces an entire index of twist bits.
This trio spans 1/4 inch up to 7/8 inch across three graduated cones, built on M35 high-speed steel with 5% cobalt. Unlike the twist-bit sets earlier in this list, these shine in thin stock where a conventional flute would grab and tear the edge.
Everyday Wins
- Three cones cover roughly two dozen hole sizes from 1/4″ to 7/8″
- Deburring happens naturally as each tier smooths the previous step
- M35 cobalt alloy handles stainless sheet better than standard HSS cones
- Supplied box keeps the tapered profiles from nicking other tools in storage
Worth Noting
- Step design suits thin material only; thick plate needs a twist bit instead
- Tapered flutes need occasional cleaning so chips don’t weld into the steps
Feature Snapshot
Built With In Mind
Electricians, HVAC installers, and auto restorers punching clean holes in gauge sheet metal.
Skip It When
Deep holes in thick steel call for the TopLine No. 7 M42 jobbers, which cut where a cone cannot reach.
Thirteen jobber-length pieces in 1/16 inch increments give a new toolbox genuine cobalt performance without the bulk of a 29-piece case. Jobber length, the standard shank-to-flute proportion, fits handheld drills and most bench presses comfortably.
The M35 blend carries 5% cobalt, enough alloy upgrade to notice on cast iron fittings and copper pipe yet forgiving enough for first-time users still learning feed pressure. Against the CaRoller kit, you trade breadth for a lighter, cheaper entry point.
Strong Points
- Thirteen incremental sizes handle most household pilot-hole needs
- 5% cobalt M35 steel outlasts plain HSS in abrasive metals
- Works across copper, aluminum, plastics, and wood, not just ferrous stock
- Compact footprint suits apartment toolkits and small garage shelves
Honest Caveats
- Smaller diameter ceiling limits bigger hardware-store tasks like lag shields
- Thin bits demand a gentle touch; owners commonly report snapping the smallest sizes under heavy feed
Core Details
Who Will Love This
First-time tool owners and casual DIYers tackling home maintenance in wood, plastic, and light metal.
Swap It Out When
Anyone needing diameters past a quarter inch should step up to the CaRoller 29-piece set for its fuller range.
What Matters Most Before Choosing M42 Cobalt Drill Bits
Match The Alloy To Your Material
M42 steel carries roughly 8% cobalt, while M35 carries about 5%. The higher share buys real heat resistance for stainless, titanium, and hardened stock. Softer metals, plastics, and lumber rarely justify the premium, and a basic HSS bit often does the same job for less money.
Hardness Cuts Both Ways
Rockwell ratings in the high 60s sound impressive, and they are, but harder steel is more brittle. Thin diameters snap under sideways force long before they dull. Handheld drilling with wobbly technique favors slightly softer M35; press work with rigid setup rewards full M42.
Size Strategy Beats Set Size
Counting pieces misleads. A machinist needs ten identical 2.0mm bits; a homeowner needs twenty-nine different ones. Buy the shape of assortment your actual projects demand rather than the biggest number on the box.
Geometry And Finish Count
Ground flutes run straighter and truer than rolled ones, which matters for tapped holes. Coatings help visibility and chip flow, though they wear off eventually. Step drills replace whole indexes for sheet work but can’t reach deep holes, so plan around both shapes.
Key Considerations Across These Picks
Traps First Timers Fall Into
The classic error is buying M42 for wood-only projects, paying for heat resistance you’ll never use. The second is running cobalt bits at full trigger speed; slow RPM and steady pressure are what let the alloy earn its keep. Skipping cutting oil on stainless wastes even good steel.
What Separates Premium From Basic
Higher-tier bits use ground-from-solid blanks, tighter hardness control, and higher cobalt percentages. Those attributes show up as straighter holes, longer intervals between sharpenings, and fewer snapped tips in production settings. Casual users may never notice the gap; daily trade users feel it within a week.
Frequently Asked Questions
What does M42 mean on a drill bit?
It identifies a high-speed steel grade containing about 8% cobalt. That addition raises hot hardness, so the cutting edge stays sharp at temperatures that soften ordinary bits.
Can cobalt bits drill through stainless steel?
Yes, and that’s their core strength. Work slowly, apply steady pressure, and use cutting oil to prevent the surface from work-hardening under the bit.
Are M42 bits too hard for wood or plastic?
They cut those materials fine, though the extra cost buys little benefit. A standard HSS set handles non-ferrous and organic materials economically.
How do I keep cobalt bits from breaking?
Avoid side load, back off pressure when breaking through thin stock, and match drill speed to bit diameter. Smaller sizes need higher RPM but gentler feed.
Do cobalt drill bits need sharpening?
Eventually, yes, though they hold an edge several times longer than plain steel. A bench grinder with a drill jig restores the original 118 or 135 degree point angle.
Closing Thoughts
Cobalt steel earns its place the moment stainless enters the picture, and any of these five handles that job honestly. Match the format to your workload, a full kit for variety, singles for repetition, steps for sheet metal, and you’ll stop burning through bits. Start with the option closest to your next project and let the results guide the rest.
