Chisels: setting it up and changing the bit or blade

Learn to set an SDS drill to chisel mode, fit or change chisel bits, and check they are locked before use.

CH-01Know the parts of the drillYou'll need an SDS drill (SDS stands for a chuck system that lets the bit move slightly in and out, which is what makes hammering work). Find three things: the chuck at the front where the bit goes, the locking collar you pull back to release it, and the mode dial, usually marked with a drill icon, a drill-plus-hammer icon, and a hammer-only icon (this last one is chisel mode). If your drill has no mode dial with a hammer-only setting, it can't do chiselling.

CH-02Pick the right chisel bitSDS chisel bits have a grooved round shank, not the smooth round or hex shank you'd see on a normal drill bit. A flat chisel bit is for scraping off tiles, old plaster or render. A pointed bit (called a bull point) is for breaking up masonry or concrete. The beginner mistake is trying to force a normal masonry drill bit into chisel mode. It won't fit the SDS chuck properly and shouldn't be used this way.

CH-03Fit the bit into the chuckWith the drill switched off and unplugged (or battery out), pull the locking collar back towards you and hold it there. Push the bit's shank fully into the chuck, turning it gently until it drops in as far as it will go. Release the collar, then give the bit a firm tug and a wiggle. It should not pull out, and it should have a small amount of side-to-side play — that's normal and lets the hammer action work.

CH-04Set the mode dial to chisel-onlyTurn the mode dial to the hammer-only icon (usually just a hammer, no drill symbol). This stops the bit spinning, so it only punches in and out. Some dials need you to press a small button in the middle while you turn them. Check the dial has clicked fully into position, not left halfway between two settings.

CH-05Check what's behind the surface before you startBefore you switch on, use a cable and pipe detector to scan the area you're about to chisel or drill. But treat the detector as a warning system, not a guarantee: it can miss cables that are buried deep, run in metal conduit, sit behind metal-backed plasterboard, or were installed outside the usual safe zones. Old or amateur wiring often ignores safe zones altogether. If you have any doubt at all, isolate the circuit at the consumer unit before you start, and turn the water off at the stopcock before cutting into anything that could carry a pipe. Expect something to be there and prove otherwise, rather than assuming it's clear because the detector said so.

CH-06Hold and use the drill correctlyGrip the main handle with your trigger hand and the side handle (if fitted) with your other hand. Rest the bit against the surface at the angle you want to cut, then squeeze the trigger and let the hammer action do the work — you're guiding it, not pushing hard. The common beginner mistake is leaning your full weight on the drill or using it like a lever to pry material off; this can snap the bit or damage the gears inside the drill.

CH-07Remove the bit safely afterwardsSwitch off and unplug the drill, or take the battery out. Pull the locking collar back and the bit should slide straight out. The tip can get hot from friction, especially after chiselling masonry, so don't touch it with bare fingers — let it cool or use a cloth.

CH-08Check you've set it up rightBefore touching anything you're working on, do a dry check: pull the trigger briefly with the bit pointing safely away from you and anyone else. In chisel mode, the bit should punch back and forth but not spin at all. If it spins, the mode dial isn't in the right position. The bit should also feel firmly locked with no wobble when you press it against a surface.

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