SDS drills explained

What is an SDS hammer drill?

In 1975 Bosch introduced the SDS drill (‘Special Direct System’) as an evolution of the conventional hammer drill.

In an SDS drill, the chuck (the part that grips the drill bit) is engineered to allow specially designed SDS drill bits to be inserted and held in place without a chuck key, unlike conventional power drills.

The indentations in the drill bit enable the bit to move freely for a short distance, increasing the hammering action significantly and allowing power to be directed more accurately and efficiently. This basic principle gives the SDS drill its main advantage over other designs such as conventional hammer drills where the entire chuck has to move back and forth which is much less efficient at delivering concentrated impact energy.

Bosch GBH36 VF-LI cordless Bosch SDS drill

What will an SDS drill do that standard power drill won’t?

A well-designed SDS-drill will tackle virtually anything – whether it’s on a building site or in the home.

They are engineered to drill through hard masonry, reinforced concrete and the hardest housebricks – without the need for the user to apply much pressure (no more grunting, no more swearing).

This can include demolition work and removing tiles and fixtures from walls.

Some SDS drills are designed for more than simply drilling holes. The higher spec models include a rotary stop feature which means they can be used for chiselling tiles and plaster off walls, etching out cable runs or sockets in walls. SDS Max drills are even equipped for demolition work.

Do I really need an SDS drill?

There’s no doubt that there are many fine non-SDS drilling options out there. For everyday DIY work or light trade situations, a standard combi drill or combi hammer drill may perform perfectly well.

SDS drills explained best sds drill for tradeFor the trade, an SDS is essential if you face medium or heavy duty situations regularly. Time is money and you can’t hang around whilst your drill bit makes hard work of concrete or firebricks.

For DIY’ers, the advantages of an SDS drill become clear when you need to sink a rawl plug into stubborn brick wall with flaking plaster and a shaky ladder. As many SDS converts will tell you, the extra cost is repaid many times over by the time saved by your drill breezing through the toughest substances.

Will an SDS drill take care of the lighter stuff too? (Wood, softer metals etc)

Yes. But you’ll need to check that your drill comes with an chuck adaptor or you’ll need to buy one (usually around £10-30). Traditionally with an SDS drill you may not have got the same levels of accuracy when drilling into lighter materials than with a rotary drill – however as technology has improved, so has the accuracy of SDS models. So much so that many tradesmen only take their SDS drill onto site.

What different modes do SDS drills operate in?

Drill only – without the hammer action, making it like a conventional drill but the max speed tends to be lower but with higher torque, delivering more power.

Drill and hammer – where the SDS comes into its own. The unique chuck design allows for greater impact and less noise than conventional hammer drills.

Hammer only without rotation – also referred to as ‘roto stop’ this option is found only more expensive models and allows the drill to complete a wider range of jobs such as demolition and breaking. Simply select the appropriate chisel attachment and you can carry out heavy duty tasks such as removing single bricks, tiller and digging out plaster for sockets. Drills with rotation stop are classed as 3 mode drills.

Are there different types of SDS hammer drills?Hitachi-DH18DSL-cordless-SDS-drill

Yes, you may come across SDS, SDS MAX, and SPLINE SHANK:

SDS or SDS Plus drills

The standard design SDS drill, using drill bits which have the trademark slotted and recessed shank (the shank is the part gripped by the chuck). The main factor to consider is that this has the smallest diameter SDS drill bits – 1-1/8 inch.

SDS MAX drills

The big brother of the SDS Plus capable of drilling larger holes up to 2 inches in diameter with longer drill bits (up to 28″ or so). Generally more power with plenty of speed and chiseling ability. The one drawback for most SDS MAX hammer drills is that they do not have a plain drilling action (i.e. non hammer) They have just two modes: hammer only or hammering with rotation.


Spline Shank SDS drills use distinctive drill bits with splines (or fins) at the end of the shank. However the chisels and other hammer tools have a hex shank which is with a deeply indented on one side to fit the the lock.

Do SDS hammer drills have any drawbacks?

Traditionally SDS drills and SDS drill bits were more expensive standard equivalents – and in many cases this is still so; however generally the prices have come down, making SDS drills affordable for both DIY and trade. Fans of SDS drills will tell you that the extra power, control and speed which drill bits can be changed is well worth shelling out any extra cash.

Remember: that you can’t use standard drill bits in an SDS drill unless you buy an adapter. Often these increase the length of the drill, and also do not allow use of the hammer mode. (However some SDS drills are sold with an extra chuck for gripping your standard drill bits).

This month’s best selling SDS drills

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