WOOD Magazine – October 01, 2019

60 WOOD magazine October 2019

Pattern and flush-trim bits

A straight bit with a bearing the same diam-

eter as the cutters can follow and create

parts the same size and shape as a template.

Secure the template to a workpiece slightly

larger than the template, then set the bit

height so the bearing rides on the template.

Which bit you choose depends on the job,

and whether you prefer or need the template

above or below the workpiece. A pattern bit,

with its bearing above the cutters, can rout a

dado following a template. It also requires

exposing the full cutter so the bearing con-

tacts the template [Photo E]; aflush-trim bit

allows you to expose only as much bit as is

needed [Photo F]. With a pattern bit, you can

rout workpieces thicker than the bit length

[Photos G, H]. You can even use the two bits in

tandem [Photo I].

Use large-diameter bits whenever possi-

ble, as they prove more stable and less prone

to breakage. Choose a small-diameter bit to

reach into tight concave curves.

A pattern bit places the bearing between the cutters and shank. The router

rides on the template.

A flush-trim bit bearing sits at the end of the bit. The router rides on the

workpiece.

After routing almost the full depth of the bit with the template in place, remove the template and ride the bearing against the freshly routed surface.

On this 2"-thick workpiece, the pattern bit reached just over half of the

thickness. To complete the cut, flip the workpiece over, mount a flush-trim bit,

and rout with the bearing riding on the previously routed edge.

Now that you know a “bit” more about

them, make sure your collection includes a

variety of these perhaps underappreciated,

but ready to perform, bits.

E F

G H

I

Template

Area cut with pattern bit

Template

Workpiece

Template

Template

Workpiece