SDS-Plus vs. SDS-Max - The SDS system has been used in Europe for a long time and has made it way over to the USA. People still question the differences between the different style slotted bit connection system. The name SDS comes from the German "Stecken - Drehen - Sichern" (Insert - Twist - Secure). In German-speaking countries, the back-formation "Spannen durch System" (Clamping System) is used, though Bosch uses "Special Direct System" for international purposes. The SDS system was designed by Bosch in 1975. The SDS chuck system was the original with SDS Plus being an improvement on the original SDS system, but remains compatible with SDS bits, and is now the most commonly seen on the market. SDS Max is designed for the heaviest masonry work and is not with SDS/SDS+ bits.
The difference in the bit is in the size, not necessarily in how each connects. While all three are shaped slightly different, the size is what separates the SDS+ from the SDS Max. SDS and SDS plus are 10 mm diameter - and interchangeable. SDS Max is 18 mm in diameter. That might not sound like much of a difference, but it is significant.
SDS & SDS Plus
SDS is about phased out and SDS Plus is what you will see in most stores. Both are used with carbide drill bits from 5/32” to 1-1/8” and thin wall carbide core bits up to 4”. There are also several types of smaller chipping and chiseling bits that work extremely well with standard SDS Rotary Hammers. In the big box stores, you will often find smaller sets of these bits along with longer bits sold singularly. The rotary hammer drills are listed in their description with the max capacity right in the title such as 1” SDS-Plus or 1-1/8” SDS-Plus. These maximum sizes are solid carbide bit capacities and should be considered when purchasing a new rotary hammer drill. While a 1-1/8” bit will fit in a ¾” SDS-Plus Rotary Hammer Drill, it is not recommended and it will be underpowered. If one was to drill 1-1/8" holes all day with a 1-1/8" SDS-Plus Rotary Hammer Drill all day, they too would find it underpowered. Think of this as a max towing capacity on a truck, running at max capacity is never going to give the user the best experience and half capacity is much better for the tool and the user.
SDS Max
SDS Max Rotary hammers are used with carbide drill bits 1/2” - 2”, thick wall carbide core bits up to 4” and thin wall up to 6”. There are also many chipping, chiseling, bushing, cutting and digging bits that work well with the SDS Max tools. Many of the demolition tools use the SDS-Max bits. These bits are normally sold at commercial outlets and the bits are normally sold alone. There is much more carbide on the SDS Max bits as the force of the hammering function is significantly greater than the SDS Plus sized drills. Again, the max size of the rotary hammer will be listed in the tool name. Be sure to get a larger tool than what is needed for the job. SDS Max rotary hammers can be very heavy and tough to use overhead all day long!
Long and Short
In short, SDS plus is designed for light duty applications and SDS Max was designed more for the professional and heavy duty applications. Be sure to properly size your tools for the tasks at hand.