From WoodworkersZone WoodWiki
The router trammel (also know as a circle cutting jig) is an jig that allows you to route a controled arc or circle. There are several manufactured models available to purchase. However they are quite easy to make in the shop.
Here is an example of a purchased trammel and two shop made ones:
To make your own you start with a board that is as wide as your router base and at least 6" longer than the radius of the circle or arc you wish to router. With the board still retangular you draw a line down the middle. Remove your router base and use it for a template to mark the center hole as well as the base mounting holes.
Example:
Next cut a thin kerf down the previously drawn line. This is done on the table saw with the fence set to distance and then raising the blade. Next you will drill the hole and cut the trammel into a teardrop shape. Next mount your router base.
To use the trammel you insert a screw that fits tightly into the kerf. The screw is then driven into the center of your circle. Use common sense, lowing the router bit a little each pass.
Here is an example of cutting an arc with the trammel:
Please feel free to ask any questions about the trammel by hitting the discussion tab at the top of the page or following this link: http://woodworkerszone.com/igits/showthread.php?t=9758
Thanks for looking.
Router-Jim
