How to Change an SDS Chuck Mechanism

In this Toolstop University guide, we’ll show you how to replace the SDS mechanism on your drill. There’s a video walking you through the steps below, if you would prefer to watch rather than read step by step.

There’s some debate over what SDS stands for, with some sources citing “Slotted Drive System” or “Special Direct System”. It’s likely, though, that SDS as a term comes from the German phrase “Steck-Dreh-Sitz”, which literally means Insert-Twist-Stay. And that’s because the technology was originally developed by the German power tool giant Bosch back in the 70s.

The idea of SDS is that the drill bit slots and twists into the chuck, locking it in place. This is important for hammer drills, particularly when drilling or chiselling in masonry.

The bit is locked into the SDS chuck thanks to a ball bearing. However, when this ball bearing becomes worn or goes missing, the bit will no longer lock in place. This is when you will need to change your SDS chuck mechanism.

Step 1: Open Up the Chuck Mechanism

Make sure your drill has been disconnected from its power source. Then pull back on the chuck’s sleeve, and using your small screwdriver, ease off the rubber cap.

Now the cap has been removed, the outer sleeve of the chuck will slide off.

Step 2: Remove the Circlip

Using the circlip pliers, squeeze the clip together then ease it up and off the chuck. This, in turn, allows you to remove the ball bearing retainer, the part of the chuck that grips the SDS bit.

Finally, in this step, remove the spring.

Step 3: Preparing the Chuck

You will be able to see the ball bearing contained in the slot of the chuck. This ball fits into the indentation on your SDS bit, locking it in place in the chuck. Once your replacement SDS chuck has been unpacked, use your grease to lubricate the shank where the new ball bearing will sit.

Step 4: Fitting the New Ball Bearing

Now fit the new spring over the shank, followed by the curved, saucer-shaped washer. At this point, insert the new ball bearing into the slot. Once in place it’ll hold the washer and spring in place. Fit the large washer on to the shank, followed by the retaining plastic washer. This washer has a groove and a raised edge. The raised edge goes down the shank first with the groove slotting over the ball bearing. Fit the last washer then the front slide, which will all be held in place via the circlip.

Step 5: Re-fitting the Circlip

Using the circlip pliers, introduce the clip to the snout of the shank, easing it apart and down onto the ringed groove. Use the small screwdriver if needed to ease it into place. Now place the plastic cap down onto the circlip at the end of the shank.

The chuck has now been reassembled! Fit an SDS bit into the chuck and you’ll find that it now locks safely into place.

Congratulations, you’ve repaired your SDS chuck! Safe drilling.