drilltools
This is a drill bit I got in a kit that included brad point bits, masonry bits and regular drill bits, all without instructions or labels.
At first, I thought the ridges were meant to make screw threads like a tap bit, but the ridges don't extend beyond the approx 1/4" diameter of the screw.
What kind of drill bit is this? What's it for?
Silestone is natural quartz aggregate, held together by a polymer binder. I believe it's something like 85% quartz. You'll need a diamond coated bit like this one; it's a tiny hole saw where the rim is covered in diamonds:
It's a bit tricky to start, you need to hold the drill at a slight angle so that only one side of the circumference is grinding, and then as you start to develop a crescent-shaped groove you gradually move your drill perpendicular and continue with the rest of the hole. If you don't do this the thing will walk all over the place since it has no positive center like a regular hole saw.
For drilling upside down you'll want a spray bottle with water to keep the surface as wet as possible. That Hitachi bit I linked to has a spiral groove going in the opposite direction of a normal drill bit, which serves to draw water into the hole, which will help you when drilling upside down.
Obviously you want to be careful not to drill too far and pop out of the top of your nice counters.
For fastening the dishwasher you'll need a plastic anchor into which to run your screws, and I've found this type works great. In a solid material the plastic will extrude around the screw threads and hold really tightly. They do sell them at my Lowe's but I can't find them on their website. The 3/16" size is probably what you need for your dishwasher, and the diamond bit I linked to above is also 3/16". Good luck!
Absolutely that will drill through concrete but you will need a SDS hammer drill which the typical home owner does not have. This is the type of drill http://www.jccayer.com/product.php?productid=1169
For such a small hole you can use a regular rotary pistol grip hammer drill with a cheap Canadian tire masonry bit to do your holes.
Best Answer
That's sometimes called a "drill-saw" bit used for drilling a hole and then enlarging the hole into a slot (or other shape) by applying sideways pressure.
I have a couple of cheap ones and didn't find them very effective in softwood. To make a long slot (1ft or 300mm) I had to drill lots of adjacent holes conventionally and then used this type of bit to join the holes. If I had to do it again, I'd consider buying a cheap router for the job. A hand jab-saw/pad-saw/keyhole-saw might be quicker and might be a similar amount of effort.