Toolsday: Forstner Bits

Twist drill bits like I reviewed last week are good for certain kinds of holes, but larger holes and special types of holes sometimes need special bits. One of my favorite types is called a "forstner bit".

Forstner Bits

These bits basically cut holes several ways at once. They scrape out a circular hole as they go down, they cut a circular hole around that, and the scrape the sides of the hole. They make a smooth-sided and mostly smooth-bottomed hole. They have a pilot point to keep the hole centered, and the cuttin action around he edge minimizes the amount of wood torn out by the spinning action.

Most people think about this bits as being for larger holes, but they are much more than that. The smallest bit here is just a quarter inch in diameter, and the largest is just an inch. I have a couple larger, and they come much larger, but forstner bits are really about that cuttin action, not just size.

I use these a lot for joinery, since the smooth sided holes take dowels and pegs nicely. They're also great for hogging out large amounts of wood from mortise before you smooth the sides with a chisel.

I used to use spade bits for thise kind of boring, but forstner bits are much more stable, and can even be used to cut holes at an agle to the surface, or overlapping an edge of the material.

They can be quite expensive, especially if you want a large bit, but I bought this set on sale. I get a lot of use out of them.

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2010.10.12 at 12:00am EDT