Popular Woodworking 2004-08 № 142, страница 49

Popular Woodworking 2004-08 № 142, страница 49

Before you rout an oval with a double trammel, decide the length of the major and minor axes, then mark them on the workpiece. Center the double trammel pivot block over the point where the major and minor axes cross (Y), aligning one sliding pivot with the major axis and the other with the minor axis. Stick the pivot block to the workpiece with double-faced carpet tape. Mount the router on the beam, align it with the major axis and position the router so the bit is at one end of the axis. Center the minor pivot (the pivot that moves along the minor axis) over point Y and fasten the beam to it.

Swing the beam 90°, aligning it with the minor axis, and position the router so the bit is at the end of that axis. Center the major pivot over point Y and fasten the beam to it. The beam should now be fastened to both pivots. To check the setup, swing the router once around the pivots with the power off. The bit should pass over the ends of the major and minor axes.

To cut the oval with this double-trammel jig, swing the router around the pivots, pulling gently outward. This slight tension will take any play out of the mechanical system as the pivots slide back and forth in their grooves. Make the cut in several passes.

A BIT OF ADVICE

A router bit consists of a cylindrical shank (1/4" or V2" in diameter) and one or more flutes or cutting wings, usually comprised of a piece of carbide brazed to the metal body of the bit. Throughout this series we have provided a closer look at many of the common and specialized bits to use with your router. The bits shown here are great when using your router for some of the more advanced applications.

Keyhole Bit

For hanging a project flush to the wall, a keyhole bit is the answer. It plunges into the wood, then plows a channel, perfectly sized to slip over a screw head.

Multi-profile Bit

\ [ One bit does it all.

By adjusting the height and the ^^^ distance to ■ the fence, this one bit cuts a variety of profiles. Mix and match the shapes. The options are limited only by your imagination and the jigs you can use.

Upspiral Bit

At first you may say this bit just plows grooves. Not true. The spiraling flutes of this bit also remove the waste from the groove, keeping the cut clean and keeping the bit from overheating and working harder than necessary.

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