Tips for drilling concrete
Tip 1: choose the right drill bit
If you're drilling concrete – with a hammer drill, of course – don't use anything but a true concrete drill bit. The differences between different drill bits are found in how they're attached – a version of SDS or quick release – and the drill head. Stone and concrete drill bits have blunt heads that act like a kind of chisels, chipping away the material. The difference between a stone and concrete drill bit is the point. On a stone drill bit, it's made of the same material as the rest of the drill bit. For a concrete drill bit, it was added later and made of tungsten carbide or widia (from the German "wie Diamant" – as diamond). That makes the point hard and perfectly suited for drilling into concrete.
Tip 2: use a depth stop
It's not just the width of your plug that's important when drilling a hole in concrete. You also measure the length to know how deep the drill hole needs to be. If you don't go deep enough, the plug won't fit. Go in too far, and it will sink in too deeply. A depth stop – standard on most hammer drills – makes sure you'll drill accurately down to the millimeter. You can of course use the measurements on the depth stop, but it's even easier to put the plug on the drill head and use it to set the depth stop.
Tip 3: look out for pipes
Hitting a water pipe or electrical wiring when drilling can have far-reaching consequences. It might even mean the entire wall has to be opened up to repair the damage. That's not something anyone wants for just trying to hang a clock in the kitchen. Luckily, hitting pipes can be avoided by using a pipe detector. It's a device that will tell you if there's metal in that part of the wall. That way, you can avoid pipes and possible rebar.
Tip 4: drill carefully when drilling tile
Sometimes, you first have to go through a layer of tables before reaching the concrete. The tiles aren't just something you quickly punch through. The risk of damaging the tile is simply too great. First, carefully drill all the way through the tile using a tile drill bit with a sharp point, and without using the hammer function. Only then use the hammer drill's full power combined with a concrete drill bit. Use masking tape on the smooth surface of the tile to prevent the drill from wandering and causing scratches.
Tip 5: get rid of dust
The difference between a neat DIY job and sloppy work is in the details. One of those details is the removal of grit and dust when drilling concrete. In order to create as neat a drill hole as you can, you should pull back the drill at a low RPM a few times. It's a great idea to use a dust collector or someone with a vacuum nozzle by the drill hole. When you've reached the required depth, slowly pull back the – still rotating – drill and use a vacuum to clean out the last bit of dust from the hole. That way, you can be sure the plug will fit.