SDS Plus vs SDS Max Which Do You Need?
If you work in construction or heavy renovation, you've almost certainly come across SDS drills and bits. But the two most common formats — SDS Plus and SDS Max — are not interchangeable. Using the wrong one doesn't just give you poor results; it can damage your equipment and slow down the job. This guide tells you exactly what each one is, when to use it, and how to choose.
What Does SDS Mean?
SDS stands for Slotted Drive System (originally from the German 'Steck-Dreh-Sitz', meaning insert-twist-stay). It refers to the shank design at the base of the drill bit — the part that slots into the chuck. Unlike standard round-shank bits, SDS bits have slots that lock into the drill's chuck, allowing the bit to move back and forth (hammer action) without slipping. This is what makes SDS drills so effective at masonry and concrete work.
SDS Plus: The Trade Standard
SDS Plus is by far the most common SDS format. It uses a 10mm shank with two open slots and two closed slots. The bit locks in but can slide axially (back and forth) to transmit the hammer blow into the material.
Best for:
• General masonry drilling (brick, block, mortar)
• Standard concrete up to medium thickness
• Everyday trade work — electricians, plumbers, joiners
• Anchoring and fixings in domestic and commercial settings
• Hole sizes from 4mm up to around 26mm
The MerTools Rocket 3 (SDS Plus) and Rocket 7 (Premium SDS Plus) are both designed for this format — suitable for the vast majority of trade applications.
SDS Max: Heavy-Duty Demolition
SDS Max uses an 18mm shank with three open slots and two closed slots. The larger shank transfers significantly more energy per blow, making it the right choice for demanding applications.
Best for:
• Breaking out floors, walls, and foundations
• Drilling large diameter holes (25mm+) in reinforced concrete
• Core drilling and chiselling
• Commercial and civil engineering work
• Demolition hammers and rotary hammers above 5kg
SDS Max bits and SDS Plus bits are NOT compatible with each other's chucks. Always check your drill's specification before ordering.
Side-by-Side Comparison
|
Feature |
SDS Plus |
SDS Max |
|
Shank diameter |
10mm |
18mm |
|
Typical drill weight |
2–5kg |
5–10kg+ |
|
Hole size range |
4mm – 26mm |
16mm – 52mm+ |
|
Best material |
Brick, block, standard concrete |
Reinforced concrete, stone |
|
Typical use |
Everyday trade & DIY |
Heavy construction & demolition |
|
MerTools range |
Rocket 3, Rocket 7 |
Rocket 5 |
Which Should You Buy?
The answer almost always comes down to your drill. Check the chuck on your rotary hammer — it will be clearly marked SDS+ or SDS Max. If you're buying a new drill alongside bits, here's a rough guide:
• SDS Plus: Light to medium trade work (electrician, plumber, general builder)
• SDS Max: Groundworks, structural drilling, concrete cutting
• SDS Plus: DIY and occasional trade jobs
If you're unsure, SDS Plus is the safer bet for most jobs. It covers the vast majority of everyday masonry drilling needs, and the bit range is much wider.