If you own a rotary hammer or SDS drill, understanding which bits fit your tool is crucial. SDS stands for Steck-Dreh-Sitz — a German term meaning “Insert-Twist-Stay” — a quick-change chuck system invented by Bosch in 1975. Today, it’s the industry standard for rotary hammers and demolition drills worldwide.
But there’s a catch: SDS bits come in three incompatible systems. A bit designed for one won’t work in another, no matter how hard you try. Using the wrong shank can damage your tool, break the bit, or create a safety hazard.
This guide covers the three main SDS systems, how to identify which one you have, and what bits are compatible with your specific tool.
Quick Compatibility Table — SDS Systems at a Glance
| System | Shank Diameter | Slot Configuration | Common Applications | Max Bit Diameter | Tool Examples |
|---|---|---|---|---|---|
| SDS-Plus | 10mm | 2 open + 2 closed slots | Drilling, chiselling, light demolition | 30mm | Bosch GSB, Makita HR2230, DeWalt D25033 |
| SDS-Max | 18mm | 3 open + 2 closed slots | Heavy demolition, core drilling | 52mm | Bosch GSH 16, Makita HM1213C, DeWalt D25899 |
| Spline Drive | 12mm (12-spline) | 12 evenly spaced splines | Older rotary hammers (phased out) | 28mm | Bosch GSH 27 (legacy), some Festool tools |
Which SDS System Do I Have?
The easiest way to identify your SDS system is to look at the chuck shank — the part of the bit that inserts into your tool.
SDS-Plus (10mm Shank)
The most common system in the UK. Look for a 10mm-diameter shaft with two deep open slots on opposite sides, plus two shallow closed slots. If your rotary hammer weighs under 10kg and was made in the last 15 years, it’s almost certainly SDS-Plus. This system fits tools from all major brands — Bosch, Makita, DeWalt, Milwaukee, Festool, Hilti — without any adaptation.
SDS-Max (18mm Shank)
The heavier-duty professional choice. The shank is noticeably thicker at 18mm, with three open slots (instead of two) and two closed slots. These tools are used for serious demolition, core drilling, and commercial construction. They’re significantly more expensive than SDS-Plus equivalents and less common in domestic toolboxes. Tools from different brands are still compatible — an SDS-Max bit from Makita works in a Bosch SDS-Max tool.
Spline Drive (12mm Shank, 12 Splines)
This is the legacy system, now being phased out. Instead of slots, the shank has 12 evenly spaced splines running along its length. You’ll only find this on older rotary hammers, typically pre-2005. Spline Drive tools are becoming harder to find, and bit availability is limited. If you’re replacing a Spline Drive tool, consider moving to SDS-Plus — the bits are cheaper and more readily available.
SDS-Plus Compatibility — The Most Common System
SDS-Plus is the workhorse of the UK construction and DIY scene. All SDS-Plus bits, regardless of brand, work in all SDS-Plus rotary hammers, regardless of brand. This universal compatibility is one of the key strengths of the standard.
The shank is a 10mm-diameter cylinder with precisely engineered slots. When you insert the bit, the tool’s chuck grips these slots via spring-loaded pins, creating both rotational drive and the push-pull action needed for hammering. Bits range from 4mm (for small precision holes) up to 30mm diameter (for large masonry holes).
Popular SDS-Plus bits include drilling bits for masonry, rotary chisels (flat and pointed), and mixing paddles. A typical homeowner or tradesperson might have a mix of 5-10 different bits covering diameters from 6mm to 25mm.
Because SDS-Plus is so universal, buying bits is straightforward — just check the shank is 10mm and SDS-Plus, and you’re done. There are no compatibility problems between brands.
SDS-Max Compatibility — Professional Heavy Duty
SDS-Max is the system for serious work. The 18mm shank is substantially thicker, with three open slots (versus two in SDS-Plus), making it stronger and capable of transmitting more energy from the hammer. Like SDS-Plus, all SDS-Max bits work in all SDS-Max tools, regardless of brand.
SDS-Max tools typically weigh 7-15kg and deliver between 10 and 20 joules of impact energy — far more than SDS-Plus tools. They’re used for breaking concrete, coring large holes, and removing stubborn masonry. Bit sizes range from 12mm up to 52mm diameter, though most everyday work stays below 40mm.
The trade-off is cost. SDS-Max bits are 2-3 times more expensive than SDS-Plus equivalents. A single 32mm SDS-Max masonry bit can cost £15-30, whereas an SDS-Plus equivalent might be £5-12. If you only need to do occasional drilling, SDS-Plus is more economical. If you’re a professional or do regular demolition work, SDS-Max is a worthwhile investment.
Spline Drive — Legacy System Being Phased Out
Spline Drive predates the modern SDS systems. Instead of slots, the shank features 12 evenly spaced splines (grooves) that run the length of the shank, creating the grip between the bit and chuck. It’s a robust system but has been superseded.
If you have a Spline Drive tool, bits are still available, but they’re becoming harder to find and typically cost slightly more than SDS-Plus equivalents. More importantly, Spline Drive tools are no longer manufactured by major brands.
If your Spline Drive tool breaks or wears out, the practical choice is to upgrade to an SDS-Plus rotary hammer. Entry-level SDS-Plus tools start around £50-80, making the upgrade affordable compared to the ongoing inconvenience of hunting for Spline Drive bits.
Can You Mix SDS Systems?
No — absolutely not. The shank sizes and slot geometries are completely different. A 10mm SDS-Plus shank will not fit in an 18mm SDS-Max chuck. Attempting to force a bit into the wrong system will damage both the bit and the tool’s chuck mechanism. Additionally, it’s a safety hazard — a misaligned bit can jam, break, or fly out during operation.
The only exception is using adapters (covered below), which convert between systems. However, adapters are workarounds and should only be used when you don’t have the right bit available — they reduce performance and are not recommended for regular use.
Using Adapters — When and Why
Adapters exist to convert between incompatible systems. The most common adapter is SDS-Plus to keyless chuck, which lets you use standard drill bits in an SDS tool. Another is SDS-Max to SDS-Plus, which allows SDS-Plus bits to be used in an SDS-Max tool.
Adapters should be viewed as emergency solutions, not routine tools. They introduce runout (wobble), reduce energy transfer, and can create safety issues. For detailed information, including a full compatibility table and when adapters are worth using, see our SDS Chuck Adapters Guide.
Brand Compatibility — Makita, DeWalt, Bosch, Milwaukee & Others
Here’s the excellent news: SDS bit compatibility is universal across brands. A Makita SDS-Plus bit works in a DeWalt SDS-Plus tool. A Bosch SDS-Max bit works in a Milwaukee SDS-Max tool. There are no proprietary variants or brand-specific shanks — the standard is truly standardised.
This means you can buy bits from whichever manufacturer offers the best price or performance for your specific need, without worrying about compatibility.
For detailed information about specific brands and their SDS systems, see:
- Makita 18V LXT Battery & Tools Compatibility
- DeWalt 20V MAX Battery & Tools Compatibility
- Milwaukee M18 Battery & Tools Compatibility
Popular SDS Bit Sets — Where to Buy
For most DIYers and tradespeople, a mixed set of SDS-Plus bits covering 5-28mm is the best starting point. Popular options include:
- Bosch 7-Piece SDS-Plus Set — classic, reliable, covers most common sizes. Buy on Amazon
- Makita Nemesis SDS-Plus Set — premium tough bits, often last longer. Buy on Amazon
- DeWalt Extreme SDS-Plus Set — good value, solid performance. Buy on Amazon
- SDS-Max 3-Piece Set (for occasional heavy work) Buy on Amazon
Watch: Video Guide
Frequently Asked Questions
Are all SDS-Plus bits really compatible across brands?
Yes. SDS-Plus is an international standard (DIN 3338) adopted by all major manufacturers. A Bosch, Makita, DeWalt, Festool, or Hilti SDS-Plus bit will work in any brand of SDS-Plus rotary hammer. The shank geometry and slot configuration are identical.
Can I use an SDS-Plus bit in an SDS-Max tool?
Not directly — they’re different shank sizes (10mm vs 18mm). You can use an SDS-Max to SDS-Plus adapter (like the Bosch HA1030), but this reduces performance and is only for emergencies. See our Adapters Guide for details.
What’s the difference between SDS-Plus and SDS-Max performance?
SDS-Max tools are heavier and deliver more impact energy, allowing them to drill larger holes (up to 52mm vs 30mm for SDS-Plus) and tackle tougher demolition work. SDS-Plus is lighter, more manoeuvrable, and suitable for everyday drilling and small chiselling tasks. See SDS-Plus vs SDS-Max for a full comparison.
Why are SDS-Plus bits cheaper than SDS-Max?
SDS-Plus bits use less material (smaller shank, less steel), and the market for them is much larger, which drives down costs through economies of scale. SDS-Max is a niche market for professional and commercial users, so bit prices remain higher.
Can I use normal drill bits with my SDS hammer?
Not directly — SDS bits have a different shank. You can use an SDS-Plus to keyless chuck adapter to fit standard drill bits, but you’ll lose the hammer action and only get rotary motion. See Can You Use SDS Bits in a Normal Drill? for details.
What size SDS-Plus bit should I buy first?
Start with 6mm, 10mm, and 16mm diameters — these cover 90% of everyday drilling tasks in masonry. If you’re chiselling, add a 20mm flat chisel. Most bit sets include a good mix of common sizes.
