What is the SDS System?

What does SDS mean?

This is a common question asked by a DIY novice. To make matters worse there are three types of these drills available: SDS Plus, SDS Top and SDS Max. This article provides a basic grounding in what the SDS system is, where it originated and what part of the system you might be interested in.

Origins of the SDS System

Bosch invented the SDS drill system in 1975. Bosch advertise SDS internationally as meaning Special Direct System, though in German speaking nations it is more usually known as Spannen Durch System(meaning “clamping system”).

Types of Chuck Available

There are three standards available:

  • SDS Plus is the smallest of the three and is a very common fitting for professional and DIY use. The tool’s shank is 10mm and inserts 40mm into the chuck. It is rated for hammers up to 4kg.
  • SDS Top is the least common of the three standards. It uses a 14mm fitting that inserts 70mm into the chuck. SDS Top is rated for hammers in the 2kg to 5kg range.
  • SDS Max is a very common industrial fitting. SDS Max employs an 18mm shank with three open grooves and a locking mechanism, instead of the two rolling balls employed in SDS Plus and SDS Top. The shank inserts 90mm into the chuck. Max is rated for hammers over 5kg and is a common fitting for light industrial use.

How Does SDS Work?

All SDS tools have a cylindrical shank with various grooves down the sides. On SDS Plus and SDS Top bits there are small grooves to provide rotary force and two closed channels for a ball roller to fit into. The ball roller allows the bit to move back and forwards freely whilst under hammer action. SDS Max employs three ball rollers.

SDS Plus tools are fitted by pressing the chuck backwards towards the body of the drill and inserting the bit. Removal is carried out in a similar fashion. SDS chucks are keyless.

Advantages of SDS

  • Quick exchange of tools
  • No chuck key required for tool exchange
  • Improved hammer action compared to normal varieties
  • Rotation Stop or Hammer Only action enables versatile use

Disadvantages of SDS

  • Cost of tools is higher than normal fittings
  • Chuck requires regular lubrication
  • Chuck must be kept clean internally else damage can ensue

In Conclusion

The SDS system gives modern power tools a versatile edge over older competitors. SDS tools are generally more powerful than their conventional cousins. Although bits used in the system are more expensive they are long lasting and durable, usually being tipped with tungsten carbide (TC) or similar material to give longer life.

SDS Plus is a very common fitting for power drills used by both professionals and serious DIY enthusiasts. SDS Top is an uncommon fitting and this may or may not be an issue to your purchase choice. SDS Max is usually a light industrial fitting only as it is used with hammers rated over 5kg. Hammers as this rating are usually used for light demolition work.