Woodworker's Journal 2007-Winter, страница 69

Offset with Laminate

W' ant a jointer in your shop? Most of us do, but not all of us have enough floor space or a big enough wallet. However, if you have a router of almost any size, you can make a jointing jig that in our opinion does some tasks better than a "real" jointer.

The secret is a spiral-flute router bit that, unlike the knives of most conventional jointers, produces tearout-free jointing on squirrely grained or bird's-eye figured wood (see page 71). Even if you do have a jointer but often work in these lovely but difficult-to-machine woods — especially in smaller dimensions — a router-jointer jig will consistently create a smoother surface. The router-jointer jig also allows you to joint clean plywood edges and other composite or even plastic materials, a task that can quickly dull the knives of a regular jointer, especially if the plys are bonded with a hard glue.

A conventional jointer will perform two operations: edge jointing and face jointing. Many of us only edge-joint because we buy our wood already surfaced (face jointed). This router jointer jig will yield smooth, accurate edges — safely, comfortably, and consistently — for the price of a long spiral bit and a few square feet of plywood. Obviously, this jig can't perform face jointing.

The setup has four components: a router, a spiral-flute bit, the table and the fence. Ideally, the router should have a 1/2" collet because larger-diameter bits run smoother and make cleaner cuts than smaller diameter bits, assuming that speed of bit rotation and feed rate are the same. However, since the amount of stock removed is so small, a junior version could be made using a router with a 1/4" collet. This limits the thickness of the wood to be jointed to stock less than 3/4", but if you are a box maker working in thinner woods, this may be just the ticket.

When you use a traditional jointer, the two beds of the tool offset to accommodate the depth of the cut you are making. On this jig, it is the fence that has the offset built into its design.

Create that offset using the thickness of the plastic laminate on the outfeed side of the fence.This same thickness determines the depth of cut.

The bit of choice has spiral flutes. Because the cutting edge of the bit's flutes are in continuous contact with the wood and presented to the wood at an angle, it always produces a chatter-free, smooth edge. Just as in hand planing, presenting an angled cutting edge to wood fibers produces a cleaner edge. An additional benefit is that the bit runs cooler, thereby staying sharp longer.

Spiral-flute router bits, now widely used in woodworking, were inspired by end mills, long used by machinists for metal-working. The

Mark the router base mounting holes by clamping the sub-base in the desired location and tapping the properly sized transfer punch with a small hammer. This impresses a small dimple in the exact center of the hole. Countersink the hole in the top table surface.

router bits come in three configurations: upcut, downcut and compression. They are available from many woodworking supply stores and web sites. Carol opts for an end mill because she uses the same bit for mortising operations, but an upcut router bit would work just fine. Either way, a 3¹/2"-long, 1/2" diameter, two-flute bit is more than adequate for most edge jointing.

The jig's table and fence are made so they may be stored by hanging on the wall or shelved when not in use.

An examination of a dedicated jointer's construction shows two flat surfaces — a split table and a fence — perpendicular to one another. It's true that a jointer's fence can be tilted, but since it is most commonly used with the fence at 90°, our router-jointing jig will be constructed to produce only 90° edges. The dedicated jointer has an infeed table and an outfeed table, separated by a cutterhead that rotates in a horizontal plane. The knives are set so they are exactly level with the outfeed table at the top of the cutting circle. The depth of cut is variable and is determined by adjusting the infeed table up or down.

The router-jointer may be seen as a modified jointer stood on its side. Its fence serves as the infeed and outfeed surfaces, and the bit rotates in a vertical plane. In the case of our jig, the depth of cut is fixed. The beauty of this configuration is that wood to be edge jointed is moved past the cutter with its wide side face down on the table. This

Winter 2007

69