Popular Woodworking 2003-10 № 136, страница 34

Ingenious Jigs

The Magic Trammel Jig

Rout precise circles and ovals without having to follow a line.

The trick to learning to cut precise, professional-looking circular and oval shapes is to achieve a "fair curve." This is a curve with no bumps, divots or abrupt changes in direction - the curve must appear to be a single, flowing line.

While you can achieve a fair curve with a band saw and a belt sander, the best tool in your shop for making a fair curve is your router. With the aid of a trammel jig, you can rout circles and ovals more precisely than you can by laying them out and cutting them with any other tool in your shop.

Making the Trammel Jig

The trammel jig consists of three parts:

• a single fixed pivot for routing circles;

• a plywood plate with two movable pivots for routing ovals;

• a long beam with a mounting plate on one end to hold the router and swing it around the two pivots.

by Nick Engler

Nick Engler, author of more than 50 books on woodworking, has built a replica of the 1903 Wright Flyer, the first true airplane.

As shown, the beam is 32" long with pivot holes spaced every V2". This lets you rout circles up to 60" in diameter and ovals up to 48" long. For larger workpieces, all you have to do is make a longer beam.

At one end of the beam, attach a router mounting plate and drill holes to mount your router. Remember, the holes must be coun-terbored or countersunk so the head of the mounting screws do not protrude.

The circle pivot block is a square block with a pilot hole in the center of one face. The oval pivot block has two dovetail slots