Drilling into stainless steel is a punishing task that turns cheap drill bits into smoking, dulled souvenirs in seconds. The work-hardening nature of the alloy demands a bit with specific cobalt content, a precise 135° split point, and the right flute geometry — anything less results in wandering, heat buildup, and broken tips.
I’m Mohammad Maruf — the founder and writer behind Gardening Beyond. I’ve spent years studying metallurgical specifications, comparing measurable hardness values, and cross-referencing aggregated owner feedback across thousands of drilling operations to isolate which bits actually handle the load.
Whether you’re punching pilot holes in a trailer frame, enlarging a sink cutout, or working with heavy-gauge plate, the bit for drilling stainless steel you choose determines whether the job takes five minutes or ends with a snapped bit and a ruined workpiece.
How To Choose The Best Bit For Drilling Stainless Steel
Stainless steel behaves differently from mild steel or aluminum. It work-hardens under friction, so a bit that barely scrapes the surface generates enough heat to anneal its own cutting edge. The right selection starts with material composition and tip geometry, then moves to length, shank design, and size range.
Material Grade — Cobalt Content Is Non-Negotiable
Standard HSS bits lack the red hardness to stay sharp when the workpiece heats up. M35 cobalt steel contains roughly 5% cobalt, which helps the bit retain hardness at elevated cutting temperatures. M42 cobalt steel, with 8% cobalt, offers even higher heat resistance but is more brittle. For general stainless work up to moderate hardness, M35 is the sweet spot.
Point Geometry — 135° Split Point Over 118°
The 135° split point reduces the axial force needed to start the cut and creates a chisel edge that self-centers on the work surface. This eliminates the need for a center punch in many cases and significantly reduces the bit’s tendency to walk across polished stainless. A standard 118° point walks more and requires a pilot dimple.
Flute Design and Shank Type
Jobber-length bits with fully ground spiral flutes clear chips efficiently from deep holes. Straight-shank bits fit standard three-jaw chucks, while hex-shank bits work with quick-change chucks and impact drivers — a major convenience for field work. Step bits with double-fluted straight grooves excel at enlarging existing holes in thin-gauge stainless.
Quick Comparison
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| Model | Category | Best For | Key Spec | Amazon |
|---|---|---|---|---|
| ZNXIMER Cobalt 16-Piece | Value Cobalt | General stainless & hardened steel | 5% Cobalt HSS, 135° Split Point | Amazon |
| NordWolf 14-Piece Metric | Metric Hex | Impact driver use on thick steel | M35 Cobalt, 1/4″ Hex Shank | Amazon |
| WildBossy M35 20-Piece | Premium Cobalt | Heavy-duty drilling, up to 1/2″ | M35 Cobalt, 3-Flat Shank, Ti Surface | Amazon |
| Jerax Tools Step Bit | Step Bit | Enlarging holes in thin stainless | M2 HSS, Double Fluted, 5 Sizes | Amazon |
| MACXCOIP Metric 19-Piece | Metric Cobalt | Precision metric work on varied metals | M35 Cobalt, 1–10mm Range | Amazon |
In‑Depth Reviews
1. ZNXIMER Cobalt Drill Bit Set
This 16-piece set from ZNXIMER uses high-speed steel with 5% cobalt, delivering the necessary red hardness for sustained stainless steel drilling. The range of 1/16″ to 3/8″ covers most household and automotive needs, and the 135° split point means you can start drilling without a center punch. Customer data shows the set reliably drills 24+ holes through steel trailer frames and mixed materials before showing measurable wear.
The fully ground spiral groove design clears chips efficiently, reducing friction heat that destroys lesser bits. One owner noted the set outperformed a local bit by a wide margin on steel. The index storage case keeps each size organized and protects the cutting edges during transport and storage.
A spark test from one user suggests the cobalt content may not be pure M35 grade, but real-world performance on wood, steel, and stainless has been overwhelmingly positive. For the price, this set offers the best balance of accessible cost and genuine cobalt capability for a wide range of stainless tasks.
What works
- Solid 24+ hole lifespan on steel trailer frames
- Storage case keeps sizes sorted
- 135° split point eliminates center punch requirement
What doesn’t
- Spark test suggests lower cobalt content than advertised
- Limited maximum size at 3/8″
2. NordWolf 14-Piece Metric Cobalt Set
The NordWolf set stands out because of its 1/4″ hex shank, which fits both standard three-jaw chucks and impact drivers. This makes it the best choice for rapid bit changes on the job. The M35 cobalt steel and 135° split point multi-blade tip deliver self-centering performance on stainless and cast iron, and the metric sizing from 1.5mm to 6.5mm covers a useful mid-range for precision fasteners.
Owner feedback highlights exceptional edge retention on thick steel and stainless, with several users describing these as the best drill bits they have ever used. The small sizes (1.5mm, 2mm) are brittle by design — drilling slightly off-angle can snap them, a trade-off common to fine cobalt bits. The storage case includes a rear hanging clip, a thoughtful touch for workshop organization.
The main drawback is value: the asking price places it above comparable SAE sets, and one customer received a partial set that required a replacement. When complete, this metric set drills stainless with authority and an impact driver-friendly shank that few competitors offer.
What works
- Hex shank fits impact drivers for fast changes
- Excellent edge retention on thick stainless
- Precise metric sizes for fastener work
What doesn’t
- Small bits prone to snapping if drilled off-angle
- Premium price compared to SAE equivalents
3. WildBossy M35 Cobalt 20-Piece Set
The WildBossy M35 set brings high-end specs to a mid-range price point: genuine 5% cobalt, a titanium surface treatment for reduced friction, and a 3-flat shank that prevents chuck slippage under heavy load. The size range spans 1/16″ up to 1/2″, giving you the largest single-bit maximum diameter in this roundup. That 1/2″ bit is invaluable for bolt-through holes and conduit entry points.
Real-world performance on hardened materials has been impressive. One owner used these bits to drill out snapped taps and studs from turbo housings — a brutal test of edge toughness. Multiple reports confirm clean cutting through thin stainless with a slow drill speed. The 135° split point keeps the bit centered without pilot dimples, and the spiral flutes evacuate chips efficiently.
Quality control appears inconsistent, however. One customer reported roughly half the set had dull bits and one snapped on the first use. The titanium coating is primarily cosmetic on a cobalt bit, but it does help identify sizes at a glance. For buyers needing the 1/2″ capacity and willing to inspect each bit before use, this set offers strong performance.
What works
- Includes a 1/2″ bit — largest in the comparison
- 3-flat shank eliminates chuck slippage
- Effective on hardened steel and stainless
What doesn’t
- Inconsistent sharpness; some bits arrive dull
- One reported bit snapped on first use
4. Jerax Tools Step Drill Bit
When the job calls for enlarging an existing hole in stainless sheet or making a clean circular cutout, a step bit is the right tool — and the Jerax Tools unit is built with M2 HSS that contains significantly more tungsten and molybdenum than standard HSS. The vacuum heat treatment and nitride surface hardening push its durability well above average step bits, and the double-fluted straight grooves produce clean, burr-free holes.
The bit offers five marked sizes from 7/8″ up to 1-3/8″, which covers sink soap dispensers, conduit knockouts, and grommet holes. Clear size highlights on the steps let you see the target diameter without stopping, saving time in production work. One electrician reported months of daily use drilling through panels and junction boxes without dulling. Another user enlarged a stainless steel sink hole using ice as a coolant and got a perfect result.
This is a specialized tool: it works best on material up to 12-gauge (2.7mm) stainless and requires steady pressure and proper RPM. It is not a replacement for a full cobalt twist-bit set when drilling deep holes in thick plate. For cutting large, clean holes in thin stainless, it outperforms everything else in the lineup.
What works
- Produces burr-free holes in thin stainless
- Color-coded steps for quick size identification
- M2 HSS with nitride treatment outlasts average step bits
What doesn’t
- Limited to 12-gauge (2.7mm) stainless thickness
- Not useful for deep hole drilling in thick material
5. MACXCOIP Metric 19-Piece M35 Set
The MACXCOIP metric set delivers a comprehensive 1mm to 10mm range in M35 cobalt steel, making it a strong entry-level option for metric-standard projects. The 135° split point and twist design provide effective self-centering on stainless, and the 19-piece count means you rarely need to reach for another set during a project. The metal index storage box offers better protection than the plastic cases found on most budget sets.
Owner feedback from a former CNC machinist confirms these bits are genuine cobalt quality, with sharp ground edges and consistent geometry. The 10mm bit alone is a rare find in affordable metric sets and is essential for M6 and M8 bolt clearance holes in stainless. The set also works well on aluminum, copper, wood, and plastics, making it versatile beyond just hardened metals.
The main concern is shank toughness — one user reported a bit slipping in the chuck and the shank getting damaged. The straight shank is uncoated and softer than premium options, so a high-quality chuck is recommended. For metric-only shops and hobbyists who need a wide range of cobalt bits at a modest investment, this set delivers genuine M35 performance.
What works
- 19-bit metric range from 1mm to 10mm
- Metal index box protects edges
- Genuine M35 cobalt, confirmed by professional users
What doesn’t
- Straight shank can slip in softer chucks
- Shank material less durable than premium brands
Hardware & Specs Guide
M35 Cobalt Steel (5% Cobalt)
The industry-standard material for drilling stainless steel. M35 retains its cutting edge at higher temperatures than standard HSS, resisting the annealing effect caused by friction against work-hardened surfaces. Look for genuine M35 rather than generic “cobalt” labels — a spark test can reveal actual cobalt content.
135° Split Point Geometry
A self-centering tip design that reduces the cutting force required to initiate the hole. The split creates two cutting edges that meet at the center, eliminating the need for a center punch on most stainless steels. Bits with a standard 118° point walk significantly more on polished stainless surfaces.
FAQ
Is a cobalt bit necessary for drilling stainless steel or can I use regular HSS?
Why does my drill bit keep walking or skating on stainless steel?
Can I use an impact driver with stainless steel drill bits?
Final Thoughts: The Verdict
For most gardeners, the bit for drilling stainless steel winner is the ZNXIMER Cobalt 16-Piece Set because it delivers genuine 5% cobalt performance, a self-centering 135° split point, and good heat management at a mid-range price that doesn’t punish experimentation. If you need impact driver compatibility and metric sizing, grab the NordWolf 14-Piece Set. And for enlarging large-diameter holes in thin stainless sheet, nothing beats the Jerax Tools Step Bit.