What is SDS Plus, SDS Top or SDS Max?
The simplest answer to this question is that they are all types of chuck system used on modern power drills. A chuck is the part of the drill that is used to hold the drill bit and in this case the drill uses SDS drill bits. It is important to note that SDS parts are not interchangeable with other conventional drill bits, or indeed each other, SDS Plus and SDS Max are not interchangeable for example. An SDS Plus drill can be fitted with a special adaptor to use normal rotary bits, though this will normally be at the cost of any hammer action the drill was capable of.
Origins of SDS Plus
The SDS drill system was originally designed by Bosch in 1975. The name SDS comes from the German “steck, dreh, sitzt” (insert, twist, fits). Bosch publicise the system on the international market as Special Direct System, although in German speaking nations it is more commonly known as “Spannen Durch System” (Clamping System).
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Bosch bits are typically classified as HC and a part number. The HC stands for hammer carbide e.g HC FC 2102 is a SDS-plus® Bulldog™Xtreme Rotary Hammer Bit. Carbide adds durability to the bits. Other codes relate to a list of different factors across the accessories range such as spline, taper, diameter, drilling depth and so on.
How SDS Plus Works (also SDS Top and SDS Max)
SDS Plus uses a cylindrical shank to hold the bit, which has indentations down its sides. The SDS tool is inserted into the chuck by pressing the collar back to open the mechanism and inserting the tool. Rotary force is applied via two or three grooves in the side of the shank. The part is allowed to move, thus allowing hammer action, as it is held in place by two ball bearings that run in the closed channels on either side of the shank. The tools bit is released by pressing the collar back toward the drill, or by pressing a release trigger, depending on the model, once this is done the part may then be slid out.
Note: SDS Max uses a locking mechanism rather than the ball bearing rollers employed by SDS Plus.
SDS Sizes and Ratings
- SDS Plus is the smallest of the three. The shank is 10mm and inserts 40mm into the chuck. It is rated for hammers up to 4kg.
- SDS Top is a rare configuration. It uses a 14mm diameter fitting that inserts 70mm into the chuck. SDS Top is rated for hammers in the 2kg to 5kg range.
- SDS Max is a common industrial fitting. It uses an 18mm shank with three open grooves instead of the two rolling balls employed in SDS Plus and SDS Top. The shank inserts 90mm into the chuck. SDS Max is rated for hammers over 5kg.
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Advantages of SDS Plus
Unlike a normal chuck where the hammer force must be absorbed by the chuck itself and SDS chuck allows the bit to move freely back and forward. This allows for a more powerful hammer action that does not destroy the tool. This system reduces the vibration experienced by an operator when drilling in masonry. Most SDS Plus drills also come with a feature called “rotation stop” or “hammer only”. This setting allows the use of accessories such as a chisel type bit for chasing cable runs, stripping plaster and light demolition etc.
The SDS system is an extremely durable, powerful and versatile development for power tools. It has become almost the defacto standard for light industrial power tools and for good reason.