About Router Bit Patterns

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By S. Baselice
eHow Contributing Writer

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Router bits are the cutting bits that fit on a router. These bits look like small, short drill bits and are usually made of steel. They have a sharp edge that cuts the wood as the bit spins, and they attach by a chuck to the router motor and drive shaft. The type of cut, or shape of the cut the router bit makes depends on the router bit pattern, which is used in conjunction with the router bit.

Basic Facts

Router bit patterns come in different thicknesses. Usually they are at least 1/8 inch thick and no more than 1/4 inch thick. This is because the router bits they are used with are not very long. They also have what is called an infield and an outfield. The infield is the cutting edge, or the edge that guides the router. This has a defined shape that is transferred to the wood when cut. The outfield is everything else, including all the space that is not cut in a pattern. Different sized outfields can be used with portable routers on large and small pieces of wood so the cut is made perpendicular to the wood.

Construction

Router bit patterns are usually made of polyethylene or hard plastic. This material is light and strong, so it can be used over and over again and is easy to carry around. It is also smooth so the router slides evenly across it and will not scratch the surface of the wood.

Types of Patterns

Patterns come in all shapes and sizes. You can buy heart patterns, curved patterns, circles, square edges and several more shapes. The size is important on closed shapes because you cannot cut a larger pattern than the size you buy. You can cut smaller patterns on a closed shape like a heart or circle by attaching a larger diameter guide to the router. This will effectively shrink the size of the final shape that you cut.

Using a Router Bit Pattern

To use a router bit pattern, you simply place it on a sheet of wood and secure it with vices or onto a router table. You then attach a router bit guide to the router. This is a circular shield that surrounds the router bit and it is used to guide the router cleanly around pattern so the bit itself does not touch the pattern and cut into it. Different sized guides are needed for different sized router bits. The inside diameter of the guide must be larger than the outside diameter of the bit. So check both to be sure before you buy them.

Other Considerations

A good router bit pattern will be very smooth on the surface and the edge. The edge pattern is the most important part; if it has bumps or cracks, it will affect your cut when the router is passed over it. However, a bumpy surface can cause just as much trouble for any user. Sliding a router across a pattern that has surface bumps or raised areas changes the orientation of the router bit, lifting it up over the wood, and tilting it at an angle which can cut into the wood and cause mistakes.