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In the Workshop: Drill Bits

Filed Under: Tools, Know-How

drill, bitsCorbis

So you've bought your brand new drill; now it's time to get some bits for boring various types of holes into your building and repair projects. If you haven't spent much time in the tool section of The Home Depot, you'll be surprised by how many types of drill bits there are. Here's a run-down of the most useful ones.

Twist bit: When you imagine a drill bit, you probably visualize the most common type: the twist bit. This is the standard cylindrical bit that's good for drilling relatively small holes into wood, metal, and plastic.

Spade bit: The business end of these bits sort of looks like the Batman symbol. They're flat with a central point and a spur at the outer edges of the 'wings.' They're ideal for drilling larger diameter holes. Spade bits tend to leave ragged edges, so they're not the best choice for finish work (see Forstner bits for that), but they're perfect for things like deck framing and running wires through studs.

Brad Point Bits: These bits are for very precise holes. In many regards they look like twist bits, but when you look closely, they actually share some characteristics with a spade bit. There is a central point which prohibits the bit from wandering as well as cutting edges on the outside of the bit. This leads to a much cleaner hole than a twist bit.

Forstner Bits
: These bits are capable of cutting a round hole with a large diameter. Because they leave a flat-bottomed hole, they're perfect for installing European hinges. If you're using a plug cutter, Forstner bits are also great for drilling out the initial hole. These bits have a little centering point and they leave a nice, clean circular cut.

Auger Bit
: These long bits are good for drilling large, deep holes in wood. They are designed in such a way that the drilled material gets forced down the flutes of the bit and ejected from the workpiece.

How the bits are constructed is also important. Some have a black-oxide coating which gives the bit some resistance to rust as well as the high heat that's generated when drilling through metal. Other bits have carbide tips which are stronger than standard bits (and they cost more too). And yet others are made of something called, 'high speed steel,' which also displays resistance to the effects of heat.

A standard drill index of twist bits start at about $15. Other, more specialized bits, like Forstner's are more expensive. Sometimes getting in the $40 per bit range.


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