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What is The Difference in Use of Small- and Large-Diameter Pattern Router Bits
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Q: I like to use a pattern bit on my router when making identical parts. One of my tool catalogs lists over 30 of these bits ranging in size from 1/4" to 1-1⁄4" in diameter. I can understand different lengths of bits to accommodate various wood thicknesses, but what’s the advantage of different bit diameters?

Differently sized pattern router bits Different sizes of pattern cutting router bits offer different cutting lines as well as allowing you to cut in tighter spaces or wider angles as needed.

A: The plethora of different pattern-bit diameters is more than a marketing ploy. I can think of several practical reasons for owning a variety of them. First, small-diameter bits are sometimes your only solution for sneaking into those tight or tiny areas of a template where a bigger bit just can’t reach. But, they’re no match for making heavy cuts or routing thick workpieces with a long bit. In these situations, larger diameter bits offer more mass and stiffness as well as a lower exit angle of the cutting flutes. Those characteristics help reduce chattering and tearout to produce a smoother cut. Whatever pattern bits you choose, look for a shear or spiral geometry when possible. They’ll give you a slicing, rather than a chiseling, action, and I’ve found that they up my odds for a cleaner cut on splintery woods and end grain.

Image #1: Different sized router bits
Image #1 Original Caption: Pattern bits come in a range of diameters to suit everything from tight-quarters work to heavy stock removal.

posted on December 1, 2009 by Chris Marshall
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