What does FDS mean?

This is a common question asked by a DIY newbie. As if that were not enough, there are three types of these drills available: SDS Plus, SDS Top and SDS Max. This article provides a basic background on 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 drilling system in 1975. Bosch advertises that SDS stands for Special Direct System internationally, although in German-speaking countries it is better known as the Spannen Durch System (meaning “clamping system”).

Available Chuck Types

There are three standards available:

• SDS Plus is the smallest of the three and is a very common accessory for professional and DIY use. The shank of the tool 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 accessory 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 accessory. SDS Max uses an 18mm stem with three open slots and a locking mechanism, instead of the two roller balls used on the SDS Plus and SDS Top. The shank inserts 90 mm into the chuck. Max is rated for hammers over 5kg and is a common accessory for light industrial use.

How does SDS work?

All SDS tools have a cylindrical shank with several grooves on the sides. On the SDS Plus and SDS Top bits there are small slots to provide rotating force and two closed channels for a ball roller to fit. The ball roller allows the bit to move back and forth freely while under hammer action. SDS Max employs three ball rollers.

SDS Plus tools are attached by pressing the chuck back toward the drill body and inserting the bit. The removal is carried out in a similar way. SDS chucks are keyless.

Advantages of SDS

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

Disadvantages of SDS

• The cost of tools is higher than normal accessories
• Chuck requires regular lubrication
• The chuck must be kept clean internally, otherwise damage may occur.

In conclusion

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

SDS Plus is a very common power drill accessory used by both professionals and serious DIY enthusiasts. SDS Top is a rare accessory and this may or may not be an issue for your purchase choice. SDS Max is typically a light industrial accessory as it is used with hammers over 5kg. Hammers in this classification are generally used for light demolition work.