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Best Drill Bits for Metal UK 2026 - Cobalt & HSS Sets Compared
Drilling into metal demands the right bit - wrong choice and you'll burn through edges in minutes. We compared five cobalt and HSS drill bit sets available on Amazon UK, from budget multi-packs to premium professional ranges, to find which ones actually hold up on stainless steel, mild steel, and aluminium.
Key Takeaways
- Best overall: Milwaukee HSS-G Red Cobalt 25pc Set - premium cobalt bits with split-point tips that stay sharp through stainless steel. Worth the investment if you drill metal regularly.
- Best value: Bosch 25x PRO Stainless Steel HSS-Co Set - purpose-built for stainless with a range of sizes from 1mm to 13mm. Hard to beat at the price.
- Best budget: PTI 25-Piece Cobalt HSS Twist Set - genuine cobalt at a fraction of premium prices. Solid for occasional metal work.
- Cobalt beats HSS for anything harder than mild steel. The 5-8% cobalt content keeps the cutting edge sharp at temperatures that destroy standard HSS bits.
- Cutting fluid is not optional. A 500ml bottle of cutting oil will double or triple the life of any drill bit set on steel. Skipping it is a false economy.
Suggested reading: Drill Bit Types Explained · Best Drill Bits for Stainless Steel · How to Drill into Brick
Quick Picks
Quick Comparison
| Product | Price | Type | Sizes | Best For |
|---|---|---|---|---|
| Milwaukee Red Cobalt 25pc | ~£35 | HSS-G Red Cobalt | 1-13mm | Stainless, hard alloys |
| Bosch PRO Stainless 25x | ~£22 | HSS-Co | 1-13mm | Stainless steel |
| Sealey AK4702 Cobalt 25pc | ~£20 | Cobalt | 1-13mm | General metal work |
| PTI 25pc Cobalt HSS | ~£15 | HSS-Co | 1-13mm | Budget metal drilling |
| UK Drills 25pc Cobalt Split Point | ~£18 | Cobalt Split Point | 1-13mm | No-centre-punch drilling |
In-Depth Reviews
1. Milwaukee HSS-G Red Cobalt Metal Drill Bit Set (25 Pieces)
~£35 | 1-13mm | HSS-G Red Cobalt | Split point
Milwaukee's Red Cobalt line uses a proprietary heat treatment that pushes the cobalt content higher than standard HSS-Co bits. The result is a bit that stays sharp significantly longer on stainless steel and hardened alloys. The 25-piece set covers every standard metric size from 1mm to 13mm, with split-point tips that self-centre without a centre punch.
In practice, these bits produce cleaner holes with less burring than budget cobalt sets. The flute geometry clears swarf efficiently, reducing the chance of chip packing on deeper holes. The downside is the price - at roughly £35, you're paying more than double what budget cobalt sets cost. But if you drill metal regularly, the extended bit life makes the maths work out.
The red-case indexing is genuinely useful - every size has a labelled slot, so you grab the right bit without hunting through a jumbled pouch. The case also keeps the bits from banging against each other, which is a surprisingly common cause of premature dulling.
Pros
- Longest-lasting cutting edge on stainless
- Split-point self-centres accurately
- Indexed case keeps sizes organised
- Clean holes with minimal burring
Cons
- Premium price for a drill bit set
- Overkill for occasional aluminium work
2. Bosch 25x PRO Stainless Steel HSS-Co Drill Bit Set
~£22 | 1-13mm | HSS-Co | PointAngle geometry
Bosch designed this set specifically for stainless steel drilling. The HSS-Co construction with their PointAngle tip geometry reduces the walking problem that plagues cheaper bits on hard surfaces. At roughly £22 for 25 pieces, it sits in the sweet spot between budget cobalt sets and premium options like Milwaukee.
The bits handle mild steel and aluminium without issue, though they're really in their element on 304 and 316 stainless. The 13mm upper limit covers most workshop needs. Bosch's quality control means every size in the set is consistent - you won't find odd bits that are slightly off-size or have rough flute edges.
One thing to note: these are not split-point bits, so you'll want a centre punch for accurate hole placement. That's a minor inconvenience for the price, and the actual drilling performance more than makes up for it.
Pros
- Specifically engineered for stainless steel
- Excellent price-to-performance ratio
- Consistent Bosch quality control
- PointAngle tip reduces walking
Cons
- Not split-point - needs centre punch
- Slightly less durable than premium cobalt on hardened steel
3. Sealey AK4702 Metric Cobalt Drill Bit Set (25 Pieces)
~£20 | 1-13mm | Cobalt | 135° split point
Sealey is a name that shows up in every UK workshop and garage, and the AK4702 set is one of their best sellers for good reason. These are proper cobalt bits with a 135° split point that drills accurately without excessive pressure. At around £20, they're priced to be replaced when they wear out rather than treasured.
The cobalt content is enough to handle stainless steel at moderate speeds, though they won't last as long as Milwaukee's premium set on sustained high-volume work. For a home workshop or occasional garage project, they're more than adequate. The split-point geometry is a genuine advantage over cheaper sets that require centre punching.
The indexing case is functional rather than fancy - a simple moulded tray that keeps sizes in order. Not as polished as Milwaukee's red case, but it does the job. Sealey also offers a decent returns policy if you get a dud, which matters when buying drill bits in bulk.
Pros
- 135° split point for accurate starting
- Well-known UK brand with decent support
- Good balance of price and durability
- Handles stainless at moderate speeds
Cons
- Case is basic compared to Milwaukee
- Won't match premium sets on sustained heavy use
4. PTI 25-Piece Cobalt HSS Twist Drill Bit Set
~£15 | 1-13mm | HSS-Co | 118° point
The PTI set is the cheapest way to get genuine cobalt drill bits in a complete metric range. At around £15 for 25 pieces, you're paying roughly 60p per bit - hard to complain about that. The HSS-Co construction handles mild steel, aluminium, and thin stainless without drama.
Where these bits fall short is on sustained hard work. The 118° point angle (compared to 135° on premium sets) means more pressure is needed to start a hole, and the cutting edges dull faster on stainless steel. For a hobbyist who drills metal a few times a month, that's perfectly acceptable. For a fabricator running through 50 holes a day, you'll want to step up to Bosch or Milwaukee.
The bits come in a simple zip-up pouch rather than an indexed case. Not ideal for organisation, but at this price point, you're buying performance not packaging. The actual cobalt quality is surprisingly consistent for a budget set - no duds or off-size bits across the range.
Pros
- Genuine cobalt at the lowest price
- Handles mild steel and aluminium well
- Consistent quality for a budget set
- Complete 1-13mm metric range
Cons
- 118° point needs more pressure to start
- Dulls faster on stainless than premium sets
- Pouch case, not indexed
5. UK Drills 25 Piece Cobalt Set 1.0mm-13.0mm Split Point
~£18 | 1-13mm | Cobalt | Split point
UK Drills is a specialist brand that focuses exclusively on drill bits - no power tools, no accessories, just cutting tools. Their 25-piece cobalt set with split-point tips is designed for metalwork, and the quality reflects that focus. The split-point geometry is genuinely sharp and self-centres reliably on steel surfaces.
The cobalt content handles stainless steel competently, and the bits maintain their edge longer than budget alternatives. At around £18, they sit between the budget PTI set and the premium Bosch/Milwaukee options - a sweet spot for workshop users who want better-than-budget performance without the premium price tag.
The indexed case is well-designed with clear size markings, and the bits are arranged in a logical progression. UK Drills also offers individual replacement bits, so you don't have to buy a whole new set when your most-used size eventually wears out. That's a thoughtful touch that shows they understand their market.
Pros
- Sharp split-point self-centres accurately
- UK specialist with individual replacements
- Good cobalt quality at mid-range price
- Well-organised indexed case
Cons
- Less brand recognition than Bosch or Milwaukee
- Not as durable as premium cobalt on hardened steel
Don't Skip the Cutting Fluid
Every set in this comparison will last significantly longer with cutting fluid. The Action Can CT-90 Cutting and Tapping Fluid is a 500ml bottle that lasts months of regular use. It reduces friction, carries away heat, and prevents the work-hardening that makes subsequent holes increasingly difficult to drill.
For thin sheet metal and aluminium, a light coat of 3-in-ONE oil works in a pinch. But for anything thicker than 3mm steel, proper cutting fluid makes the difference between a clean hole and a burnt-out bit. The maths is simple: a £10 bottle of cutting fluid can double the life of a £35 drill bit set.
Get Cutting Fluid on Amazon UK →How to Choose Drill Bits for Metal
Cobalt vs HSS vs Titanium
HSS (High Speed Steel) is the baseline for metal drilling. It handles mild steel, aluminium, and brass at moderate speeds. Standard HSS bits are fine for occasional work, but they dull quickly on stainless steel or hardened alloys.
Cobalt (HSS-Co) adds 5-8% cobalt to the steel, raising the hardness and heat resistance significantly. This is the go-to choice for stainless steel, cast iron, and tough alloys. Cobalt bits cost more but last much longer on hard materials - the premium pays for itself quickly.
Titanium-coated bits are HSS with a thin titanium nitride coating. The coating reduces friction and adds surface hardness, but it wears off relatively quickly. Under the coating, you're still drilling with HSS. Fine for light work, but not a substitute for cobalt on demanding jobs. See our drill bit types guide for the full breakdown.
Split Point vs Brad Point vs 118°
The tip geometry matters more than most people realise. A 135° split point self-centres on the workpiece without needing a centre punch - the split creates two cutting edges that bite into the surface immediately. This is the standard for metal drilling.
A 118° conventional point is cheaper to manufacture but wanders more on hard surfaces. You'll need a centre punch every time, and even then, accuracy suffers on curved or uneven surfaces.
Brad points are for wood only - the sharp central spike grips wood fibres but will dull instantly on metal. Never use a brad-point bit on steel.
Speed and Technique
Drilling metal is about patience, not force. Run your drill at 1,000-1,500 RPM for small bits (3-6mm) and drop to 500-800 RPM for larger ones (10mm+). If you see blue discoloration on the swarf or the bit itself, you're going too fast - that's heat damage happening in real time.
Apply steady, moderate pressure. Let the bit do the cutting. If you're pushing hard enough to flex the drill, you'll snap the bit. And always use cutting fluid on anything thicker than thin sheet metal. We wrote more about this in our drilling into masonry guide - the principles of speed, pressure, and cooling apply across all hard materials.
Size Range
Every set in this comparison covers 1-13mm, which handles the vast majority of workshop needs. If you regularly drill larger holes, you'll need individual bits or a step drill. For most DIY and light fabrication work, the 1-13mm range is everything you need.
Frequently Asked Questions
Final Verdict
For most UK makers and DIYers, the Bosch 25x PRO Stainless set hits the sweet spot. It's purpose-built for the hardest common drilling task (stainless steel), priced fairly, and backed by Bosch's quality control. If you drill metal regularly enough to justify the premium, the Milwaukee Red Cobalt set will outlast everything else in this comparison.
Whatever set you choose, pair it with proper cutting fluid and sensible drilling speeds. A £15 set used correctly will outperform a £35 set used dry and at full trigger. The technique matters as much as the tool.
For a deeper dive into bit geometry and material science, read our drill bit types explained guide. And if stainless steel is your specific challenge, our stainless steel drill bit guide goes into more detail on that material's quirks.
Last reviewed: August 25, 2026 · Evidence-based review · Contains affiliate links