SDS: Decoded

SDS, Plus, Max, Spline, Hex…what’s the deal? Why are there so many different options? Which one do I need? While selling tools, I have heard these questions probably more often than any other, so I’ll try to break it down for you here.

In the beginning, there was SDS. Bosch introduced the Special Direct System (SDS) Drills to the market in 1975, and since then all the other major manufacturers have gotten on board with their own SDS compatible versions. SDS tools differ from regular hammer drills because the drill bit hammers within the chuck as opposed to the entire chuck moving. This provides for more efficient operation and more power than conventional hammer drills.

Next came the evolution of SDS to SDS Plus. SDS Plus bits work in both plus and standard SDS drills. SDS and SDS plus bits are 10mm shanks inserted 40mm into the chuck.

After Plus came SDS Max. SDS Max drills are even more heavy duty that the SDS Plus. They use an 18mm Shank and are inserted 90mm into the drill chuck. The bits are not compatible with SDS plus, but Plus bits can be used in a Max drill with an adapter.

Also there is Spline. Spline tools technically don’t use the SDS system but have very similar specs and uses to the SDS max tools. The bits are not cross compatible but adapters are available to interchange spline and max bits.

So, after these explanations, which one do you need? The tool, either in their name or product description, will say, for example; “Bosch 11224VSR 7/8-in SDS-Plus Bulldog Rotary Hammer”. What this means broken down is: Bosch = Brand, 11224= model number, VSR=Variable Speed Reversing, 7/8-in =max through hole diameter in concrete, SDS-plus = type of bits accepted, and rotary hammer= the tool will drill, hammer drill, or hammer only. But what does this mean for you?

The max through hole diameter, the type of bit accepted, and the type of tool are the most important things you need to know. If you often need to drill 2″ holes through floors or walls to push conduit through, you need a drill rated at 2″, but if you only drill 5/8″ holes for anchors, you can buy a drill with a lower max through hole diameter, because you don’t need as much power or torque. Similarly, the SDS-plus is a lighter duty tool than SDS-max and provides less torque and less power for a lighter duty job, where SDS-Max is heavy duty for serious drilling or demolition. Finally there is the type of tool; Most rotary hammers will drill, hammer drill or chisel, but a demo hammer will only chisel but not drill.

Last but not least, there are Hex hammers. These tools like spline drives are not technically SDS but provide a similar function. Hex bits are used for heavy demolition in breaker hammers and demo hammers and are not for drilling. They are available in 3/4″ and 1 1/8″ shanks. The 1 1/8″ hex bit is the size most commonly used in jack hammers in the 35-80 lb class.

I hope this helps clarify the differences in the tools and bits available, but if you still have any questions, feel free to leave them in the comments below.

Click here to see the full line of Bosch SDS Rotary Hammers.

Click here to see the full line of Bosch SDS Bits and Chisels.