TIMBER FRAMING WITH THE ROUTER

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y first encounter with timber framing was 13 years ago, when a friend enlist­ed me on raising day to help him erect the frame that he had spent the bet­ter part of the summer carving. It was a 2,500-square-foot saltbox with a one-story shed on one of the gable ends. At the end of the day I stood in awe at the magnifi­cent structure before us. Timber frames are their most spectacular at this point. Standing alone, the visual appearance of the frame exudes strength and durability.

As we closed in the house over the next few months, I had numerous occasions to admire the joinery and contemplate simpler methods of mortising. Where the tenon work demands no more than a circular saw and the occasional hand saw when the depth of cut exceeds the power tool’s limit, mortising the traditional way requires hours of mallet and chisel work. 1 knew that with routers I could accomplish the task quicker and probably more accurately.

Timbers for a frame are normally rough sawn, so mortises can vary considerably for similarly dimensioned timber, creating the need for a jig design with a high degree of flexibility. With a very simple jig made from ‘A-inch-thick aluminum angle, 1 can quickly set up to rout an infinite variety of mortise sizes. The basic requirement is to extend the bearing surface beyond the edge of the timber to allow guide fences to be clamped, and to provide support for the router base.

I do the bulk of my mortising with ‘/’-inch straight bits, leaving a ‘A-inch radius on the corners. Rather than square all these corners with a chisel I’ve found it easi­er to grind the radius on the tenons and corners of the beams to be housed. On deeper mortises—up to 3’A inches—two different-length bits must be used. The degree of accuracy and precision achieved with the routers allows cleaner mortises that are truly perpendicular to the surface. This pays off when fitting knee braces and tightening the frame prior to pegging. The accuracy of the knee braces in par­ticular is critical to the alignment and structural integrity of the frame.

Being able to mortise simply and quickly, even through large knots, makes it easy to fully house all tenons, increasing the overall strength of the frame and giving a cleaner look to the joinery. In a typical frame there can be 200 to 300 mortises. With routers 1 can cut my mortising time in half or better. That adds up to a substantial saving in the production of a frame, and the joints’ greater precision makes a much more pleasant raising day.

The router is arguably the most versatile and effi­cient power tool in the mod­ern woodshop. A standard fixed-base router with a straight bit can plow rabbets, grooves, and dadoes in seconds. Fitted with an edge-forming bit, the tool can round over a tabletop or shape a piece of elaborate molding. Coupled with a jig, the router turns into a joint­making dynamo, capable of producing dovetails, box joints, or mortise-and-tenons with more speed and precision than virtually any other single tool in the shop.

Many of these tasks once required hours of laborious hand work. Although some traditionalists bemoan the fact that the router has motorized the pleasure out of many woodworking tasks, others see it as a tool of liberation. The router’s system of bits, cutters, and accessories has freed the modem woodworker from the arduous monotony of many repetitive procedures.

This chapter is an introduction to the two major types of routers on the market and a survey of some helpful com­
mercial jigs that expand the tools’ capabilities. Whether you choose a fixed-base router or a plunge model—or both— selecting the best tool to suit your particular needs is of paramount importance. The relative strengths and weak­nesses of the two types are dis­cussed on page 14.

Whichever tool you decide to select, make sure the motor is capable of at least 1 horse­power. Also, spend the few extra dollars for a tool with adjustable speed—large-diam­eter cutters work best at slow speeds, while smaller-diameter bits operate better at high speeds.

While routers do not generally require much maintenance, the steps for keeping them working safely and accurately are easy to perform. The chapter explains, for example, how to check the collet for runout (page 18). The chapter concludes with a few general principles on making basic edge-forming and grooving cuts—the foundations of the advanced operations that are covered in detail in later chapters.

іі Fitted with a piloted three-wing slotting cutter, a

router plows a groove in the edge of a board. The ^ cutter’s pilot bearing rides along the stock to ensure that the cutting depth remains uniform.

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CHECKING FOR COLLET RUNOUT

Using a dial indicator and magnetic base

Install a centering pin in the router as you would a bit and set the tool upside down on a metal surface, such as a table saw. Connect a dial indicator to a magnetic base and place the base next to the router. Turn on the magnet and position the router so the centering pin contacts the plunger of the dial indicator. Calibrate the dial indicator to zero following the manufac­turer’s instructions. Then turn the shaft of the router by hand to rotate the centering pin (right). The dial indicator will register collet runout—the amount of wobble that the collet is giving the bit. If the runout exceeds 0.005 inches, replace the collet.

Whether you are shaping the edges of a tabletop with a decorative bit or routing a recess in the middle of a workpiece for a piece of inlay, all cuts with a router are guided by the same basic principles. For starters, the speed at which the bit rotates depends on the size of the cutter. As shown in the chart below, the larger the bit, the slower the bit rotation should be. Always adjust the speed dial on your router to suit the bit diameter before starting a rout­ing operation.

Feed direction is another important consideration in router work. Proper technique will help you maintain con­trol of the tool. As a rule, the router should be moved against the direction of bit rotation, or from left to right when facing the work’s edge, as shown in the illustration below.

BASIC ROUTING

Shaping an edge with a piloted bit

Clamp down the workpiece with the edge to be shaped extending off the work sur­face by a few inches. Gripping the router firmly with both hands, set its sub-base on the workpiece with the bit clear of the stock. Turn on the tool and guide the bit into the workpiece until the pilot bearing contacts the stock, keeping the sub­base flat on the surface and the bearing flush against the edge (above).

SHOP TIP

Setting the cutting depth on a plunge router

Make a series of wood blocks so the thickness of each one equals a cutting depth you commonly use. Then position the shortest stop screw on the turret stop directly under the depth stop bar. Seat the bar on the stop screw, then push the motor down until the bit con­tacts the workpiece. Next, raise the stop bar and slip the appropriate block between the bar and the stop screw (right).

Tighten the depth stop bar clamp and loosen the plunge lock lever, allowing the bit to spring back up.

When you plunge the bit into the stock, it will penetrate until the stop bar contacts the stop screw—a distance equal to the thickness of tne wood block.

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