The standard drill bit works well with wood, aluminum, and most steels, but there are some materials that shouldn't be cut with it. In particular, very hard materials like hardened steel are inappropriate.

And there are other materials that don't seem hard, but still cause problems. PC boards are a good example of these. They look relatively soft, so you'd think they would be easy to drill, but they have fiberglass in them, which is very abrasive. Using a regular high-speed steel drill will work for a couple of holes, but the fiberglass will start abrading away the cutting edge of the drill. This will force you to push harder to drill each hole, which will produce more heat, and cause the bit to wear down more.

The correct drill bit to use on hard materials is made from Tungsten carbide. It's much harder than a standard drill; it's capable of drilling hundreds or even thousands of holes in abrasive materials or hard materials like fiberglass or hardened steel. In fact, carbide drills are the drill used by commercial circuit board manufacturers to drill holes.

On a standard drill bit, the purpose of the helix is to remove the chips as they're cut. But this can be a problem when cutting plastics because the high helix angle will work like a screw, digging into the part, and maybe causing the workpiece to be pulled out of the vice.

There is a special set of drill bits for plastics. Look at the picture above. The drill bit on the left is the more common bit, and the one on the right is better for cutting plastic. You can see that the plastic drill has a lower helix angle, which means that this drill does more scraping than cutting. It's not as efficient at removing chips, but it allows you to safely drill materials that would tend to be lifted up by other drill bits.