Stainless steel is tough on purpose. According to a National Bureau of Standards manual on stainless steel, every stainless grade contains at least 10 percent chromium. The same manual notes that its chromium-nickel grades harden only through cold working.
In practice, that means a dull or slow-cutting bit makes the metal harder as it rubs. The hole stalls, the tip overheats, and a cheap bit is done in a few holes. Solid cobalt bits keep their hardness at higher heat, so they keep cutting where plain steel quits.
For this guide to the best drill bits for stainless steel, we compared six twist sets and one step bit. We reviewed manufacturer specs, owner feedback, and alloy grades, and kept only solid M35 and M42 cobalt. Below, you’ll find our top pick, a metric option, a budget set, and the caveats worth knowing.
| Image | Title | Best For | Link |
|---|---|---|---|
 | BOSCH CO21B 21-Piece Cobalt M42 Drill Bit Set with Case | The all-round 8% cobalt M42 set for stainless, cast iron and titanium, with split points and three-flat shanks | View on Amazon |
 | STROTON Metric M42 8% Cobalt Twist Drill Bits Set, 1.5 to 6.5mm, 13 Pieces | Metric M42 bits from 1.5 to 6.5mm, including common rivet sizes for stainless panels and brackets | View on Amazon |
 | COMOWARE 21-Piece M42 Cobalt Drill Bit Set, 1/16 to 1/2 Inch | A great value 21-piece M42 set with 135° split points on every bit and an indexed case | View on Amazon |
 | STROTON Metric 5% Cobalt Step Drill Bit, 4 to 32mm, 15 Steps | Clean 4 to 32mm holes in thin stainless sheet, sinks and electrical boxes with one cobalt step bit | View on Amazon |
 | BOSCH CO14B 14-Piece Cobalt M42 Drill Bit Set with Case | A compact Bosch M42 kit from 1/16 to 1/2 inch for truck boxes and service calls | View on Amazon |
 | MACXCOIP 13-Piece M35 Cobalt Drill Bit Set, 1/16 to 1/4 Inch | A budget M35 starter set in 1/64 inch steps for occasional stainless jobs | View on Amazon |
 | STROTON 17-Piece M35 Cobalt Drill Bit Set, 1/16 to 1/2 Inch | A mid-tier M35 set to 1/2 inch with spare copies of the small bits that snap most | View on Amazon |
Solid Cobalt vs. Cobalt Coated: Why It Matters on Stainless
Stainless steel work hardens. If a bit rubs instead of cutting, the surface gets harder than the bit, and the hole stalls.
Solid cobalt bits mix cobalt into the steel itself, so they stay hard when the tip gets hot. M35 carries about 5% cobalt, and M42 carries about 8%. Coated bits only have a thin surface layer, and once it wears through, you’re drilling with ordinary steel.
That’s why every pick on our list is M35 or M42 all the way through. Don’t be fooled by the label if a listing says “cobalt” without naming the grade.
Our Picks for the Best Drill Bits for Stainless Steel
BOSCH CO21B 21-Piece Cobalt M42 Drill Bit Set with Case
View on AmazonBosch built the CO21B around M42 steel with 8% cobalt, the grade machinists reach for on stainless. The cobalt runs through the whole bit, not just a surface layer. That means you can resharpen these and keep the heat resistance.
The design details matter more than the piece count. Bits from 1/8 inch up get a split point, so they start without skating on polished stainless. From 3/16 inch up, a three-flat shank stops the bit from spinning in a keyless chuck.
We also like the doubles. You get two each of 1/16, 5/64, 1/8, 3/16, and 1/4 inch, the sizes that snap first. Heads up here: the smallest bits skip the split point, so a center punch still helps.
The most common complaint we found in owner feedback is burned tips from running too fast. That’s a technique issue, not a Bosch flaw, and it applies to every bit on this list.
What We Like
- Solid M42 alloy that can be resharpened
- Split points start cleanly without a punch
- Three-flat shanks resist chuck slip
- Spares of the five sizes that break most
- Covers up to 1/2 inch
Worth Noting
- Bits below 1/8 inch use a standard point
- Fractional sizes only, no metric
- Bigger gaps above 1/4 inch
- Premium positioning next to off-brand sets
STROTON Metric M42 8% Cobalt Twist Drill Bits Set, 1.5 to 6.5mm, 13 Pieces
View on AmazonThis STROTON kit makes sense if your plans, fasteners, or rivets are metric. It uses M42 steel with 8% cobalt, and STROTON claims 68 to 70 HRC hardness. That puts it in the same alloy class as the Bosch sets.
The size mix is the clever part. Alongside round sizes, it includes 3.2mm and 4.8mm, which match common blind rivet diameters. If you rivet stainless brackets or panels, that saves a trip to the hardware store.
Each bit has a 135° split point and a straight round shank. Heads up here: the same listing also sells a 19-piece 1 to 10mm kit. Confirm which size option is selected before you check out.
Owners mostly praise how long the small bits stay sharp in stainless. The catch is that thin M42 bits are brittle, so any side load will snap them.
What We Like
- Includes rivet-friendly 3.2mm and 4.8mm sizes
- Full M42 alloy at a friendly tier
- Split points on every size
- A bigger 1 to 10mm kit sits on the same listing
Worth Noting
- This kit tops out at 6.5mm
- Round shanks can slip in worn chucks
- Small bits are brittle under side load
COMOWARE 21-Piece M42 Cobalt Drill Bit Set, 1/16 to 1/2 Inch
COMOWARE 21-Piece M42 Cobalt Drill Bit Set, 1/16 to 1/2 Inch
View on AmazonCOMOWARE’s 21-piece set is our pick if you want full M42 coverage without big brand positioning. It runs from 1/16 to 1/2 inch in solid 8% cobalt steel. The oxide finish is cosmetic, so the cutting performance comes from the alloy itself.
Every bit gets a 135° split point, and that matters on stainless. The flatter, self-centering tip bites before the metal can glaze over. That’s how you avoid the work-hardened spot that kills cheaper bits.
The indexed case keeps sizes in order, which sounds minor until you’re hunting for 13/64 mid-job. Heads up here: the shanks are round, not three-flat. On a cordless drill with a tired chuck, the larger bits can spin.
Third party roundups we checked group this set with Bosch and Drill America as a strong M42 option. That lines up with what we see in the specs.
What We Like
- Great value for solid M42 steel
- Split point on every size
- Indexed case keeps sizes organized
- Reaches 1/2 inch
Worth Noting
- Round shanks, no three-flat grip
- Shorter brand track record than Bosch
- Fractional sizes only
STROTON Metric 5% Cobalt Step Drill Bit, 4 to 32mm, 15 Steps
STROTON Metric 5% Cobalt Step Drill Bit, 4 to 32mm, 15 Steps
View on AmazonTwist bits struggle with large holes in thin stainless sheet. They grab, tear, and often leave a triangle instead of a circle. This STROTON step bit cuts 15 clean sizes from 4 to 32mm with one tool.
It’s made from 5% cobalt steel, the M35 grade. That makes it a strong fit for electrical boxes, sink cutouts, range hoods, and stainless panels. Each step also eases the edge of the hole, so you file less afterward.
Heads up here: STROTON rates it for stainless sheet up to 2mm with a hand drill. With a drill press, that rises to 5mm. Beyond that, a twist bit or hole saw is the better tool.
Run it slow and oil every step. Step bits heat up fast because so much cutting edge touches the metal at once.
What We Like
- One bit replaces 15 twist bits for sheet work
- Round, clean holes in thin stainless
- Less burr cleanup afterward
- Ideal for conduit and panel openings
Worth Noting
- Thin material only
- Metric steps only
- Needs low speed and steady oil on stainless
BOSCH CO14B 14-Piece Cobalt M42 Drill Bit Set with Case
BOSCH CO14B 14-Piece Cobalt M42 Drill Bit Set with Case
View on AmazonThe CO14B uses the same alloy and geometry as our top pick, in a smaller kit. You get 8% cobalt M42 steel, split points from 1/8 inch, and three-flat shanks from 3/16 inch.
The size list is lean but practical: 1/16 through 1/2 inch, with a spare 1/8 inch bit. It drops in-between sizes like 11/64 and 13/64. For most repair and fabrication work, we rarely miss them.
This is the set we’d toss in a truck or service bag. The case stays slim, and every bit earns its slot.
Heads up here: one spare bit isn’t much if you drill a lot of 1/4 inch holes. Grab a few singles in your most-used size.
What We Like
- Same Bosch M42 build as the CO21B
- Slim case for mobile work
- Still reaches 1/2 inch
- Includes a spare 1/8 inch pilot size
Worth Noting
- Fewer in-between sizes
- Only one duplicate bit
- Fractional sizes only
MACXCOIP 13-Piece M35 Cobalt Drill Bit Set, 1/16 to 1/4 Inch
MACXCOIP 13-Piece M35 Cobalt Drill Bit Set, 1/16 to 1/4 Inch
View on AmazonNot every stainless job needs M42. For a few holes in brackets, hinges, or appliance panels, this MACXCOIP M35 set is plenty.
It covers 1/16 to 1/4 inch in 1/64 inch steps, all 13 sizes in an index case. The bits use a 135° point and an uncoated finish. M35 holds up to heat well, just not for as long as M42.
This is the set we’d hand a new DIYer who keeps burning up black oxide bits. It’s also one of the most widely rated budget M35 sets we checked.
Heads up here: it stops at 1/4 inch. At this tier, expect a little more variation in sharpness from bit to bit.
What We Like
- Great value for a real cobalt grade
- Every 1/64 inch size in the small range
- Index case with marked slots
- Big step up from plain HSS bits
Worth Noting
- Maximum size is 1/4 inch
- No duplicates of small sizes
- M35 wears faster than M42 in heavy use
STROTON 17-Piece M35 Cobalt Drill Bit Set, 1/16 to 1/2 Inch
STROTON 17-Piece M35 Cobalt Drill Bit Set, 1/16 to 1/2 Inch
View on AmazonSTROTON’s 17-piece M35 set fills the gap between budget kits and full M42 sets. It runs from 1/16 to 1/2 inch and includes doubles of the sizes that break most.
You get two each of 1/16, 3/32, 1/8, and 1/4 inch. Bits from 1/4 inch up switch to a three-flat shank, which helps on larger holes. STROTON also lists a 135° split point and 69 HRC hardness.
Heads up here: the listing describes the cobalt content as 5% in one place and 6% in another. Either way, it’s M35 grade, not M42. Treat it as a solid mid-tier set, not a production tool.
The four spare small bits are the real draw. Thin bits snap on stainless more than any other size, and a backup keeps the job moving.
What We Like
- Spares of four commonly broken sizes
- Reaches 1/2 inch
- Three-flat shanks on the larger bits
- Good value for the size range
Worth Noting
- M35, not M42
- Skips many in-between 1/64 sizes
- Mixed cobalt figures on the listing
Comparing the Best Drill Bits for Stainless Steel
Here’s how all seven stack up on the specs that matter most for stainless.
| Model | Type | Steel Grade | Pieces | Size Range | Point | Shank |
|---|---|---|---|---|---|---|
| BOSCH CO21B 21-Piece Cobalt M42 Drill Bit Set with Case | Twist, jobber | M42, 8% cobalt | 21 | 1/16 to 1/2 inch | Split, 1/8 inch and up | Three-flat, 3/16 inch and up |
| STROTON Metric M42 8% Cobalt Twist Drill Bits Set, 1.5 to 6.5mm, 13 Pieces | Twist | M42, 8% cobalt | 13 | 1.5 to 6.5mm | 135° split | Round |
| COMOWARE 21-Piece M42 Cobalt Drill Bit Set, 1/16 to 1/2 Inch | Twist, jobber | M42, 8% cobalt | 21 | 1/16 to 1/2 inch | 135° split | Round |
| STROTON Metric 5% Cobalt Step Drill Bit, 4 to 32mm, 15 Steps | Step | M35, 5% cobalt | 1 (15 steps) | 4 to 32mm | Step tip | Straight |
| BOSCH CO14B 14-Piece Cobalt M42 Drill Bit Set with Case | Twist, jobber | M42, 8% cobalt | 14 | 1/16 to 1/2 inch | Split, 1/8 inch and up | Three-flat, 3/16 inch and up |
| MACXCOIP 13-Piece M35 Cobalt Drill Bit Set, 1/16 to 1/4 Inch | Twist, jobber | M35 cobalt HSS | 13 | 1/16 to 1/4 inch | 135° | Round |
| STROTON 17-Piece M35 Cobalt Drill Bit Set, 1/16 to 1/2 Inch | Twist | M35 cobalt HSS | 17 | 1/16 to 1/2 inch | 135° split | Round, three-flat from 1/4 inch |
Buyer’s Guide: How to Choose the Best Drill Bits for Stainless Steel
Stainless punishes the wrong bit fast. Here’s what we look for before we trust a set on a stainless job.
1. Steel Grade: M42 vs. M35 vs. Coated HSS
M42 carries about 8% cobalt and holds its edge longest when the tip gets hot. M35 carries about 5% and is a solid step up from plain high speed steel.
We’d skip anything that says “cobalt coated” or doesn’t name a grade. The coating wears through, and the steel underneath can’t handle stainless.
2. Point Angle and Split Points
A 135° point is flatter than the common 118° tip, so it bites into hard metal faster. A split point adds small cutting edges at the center, which stops the bit from walking.
On polished stainless, a split point often means you can skip the center punch.
3. Shank Style
Stainless takes real feed pressure, and that torque can spin a round shank in the chuck. Three-flat shanks give the jaws flat faces to grip.
With round shanks, we use a keyed chuck or tighten a keyless chuck hard before each hole.
4. Size Range and Duplicates
Most stainless jobs live between 1/8 and 1/4 inch, so that range should be well covered. Spares of the small sizes are worth more than odd large sizes you’ll rarely use.
We also like sets that reach 1/2 inch for anchor holes and bolt clearance.
5. Twist Bits vs. Step Bits
Twist bits are the right tool for thick stock, brackets, and anything over a few millimeters. Step bits shine on thin sheet, where twist bits grab and leave ragged holes.
For sinks, panels, and electrical boxes, we’d keep both on hand.
6. Fractional or Metric
Match the bit system to your fasteners. If you work with metric rivets, screws, or plans, a metric set avoids loose or binding holes.
For general shop work in the US, fractional sets are easier to pair with common hardware.
Pro Tip: Slow Down, Push Hard, Keep It Wet
The biggest mistake we see on stainless is high speed with light pressure. The bit rubs, the metal work hardens, and the hole stops dead.
For a 1/4 inch cobalt bit, aim for roughly 500 to 750 RPM with firm, steady feed. Keep cutting oil on the tip the whole time.
- You want curled chips, not fine dust.
- If the bit squeals or the chips turn blue, back off the speed.
- Never let the bit dwell without cutting, since that hardens the spot.
- Drill a 1/8 inch pilot first for holes over 1/4 inch.
FAQ About the Best Drill Bits for Stainless Steel
What are the best drill bits for stainless steel?
Solid cobalt bits in the M42 or M35 grade are the best drill bits for stainless steel. Our top overall pick is the BOSCH CO21B, thanks to its M42 alloy, split points, and three-flat shanks.
Is M42 better than M35 for stainless steel?
For frequent stainless work, yes. M42’s extra cobalt keeps the edge hard at higher temperatures, so it lasts longer. For occasional jobs, M35 does the work fine and is easier on the budget.
What speed should you drill stainless steel at?
Go slower than you think. For a 1/4 inch cobalt bit, roughly 500 to 750 RPM works well, and larger bits need even less. Firm pressure matters as much as speed.
Do you really need cutting oil for stainless?
We’d never drill stainless dry. Cutting oil pulls heat out of the tip and helps chips clear, which protects both the bit and the hole. Even a few drops per hole makes a clear difference.
Why did the bit stop cutting halfway through?
That’s usually work hardening. When a bit rubs instead of cutting, the stainless surface hardens and the bit can’t bite. Raise the feed pressure, lower the speed, and switch to a sharp bit if the edge is gone.
Can a step bit go through thick stainless steel?
Not well. Our STROTON pick is rated for 2mm stainless with a hand drill and 5mm with a drill press. For thicker plate, a twist bit or hole saw is the better choice.
Can cobalt drill bits be sharpened?
Yes, and that’s a big advantage over coated bits. Because the cobalt runs through the whole bit, a fresh grind keeps the same heat resistance. Keep the 135° angle and split point when you regrind.
Are titanium coated bits good for stainless steel?
Titanium coated HSS bits handle a few holes but wear quickly on stainless. Once the coating is gone, the base steel struggles with the heat. We’d choose solid cobalt for anything beyond a one-off job.
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