Popular Woodworking 2008-12 № 173, страница 59

finished, the slot has smooth sides. (You can touch up the sides with a rasp or file if you need to.)

Two Side Pieces Complete the Jig

For step two, position two additional scrap pieces on either face of t he material to be mortised while holding one end of each piece flush with the end of the workpiece. Next, clamp the three pieces into a bench vise. These scraps or side pieces should be nearly as long as the slotted top piece of the jig.

The key to building this jig straight and centered is in the final step. Lay out the mortise on your workpiece: 1 find it best to do the layout work using the overall length of the slot, keeping in mind that my finished mortise will be V2" shorter. Position the plywood piece on the three pieces in your vise, align the slot with the layout lines at the top and bottom, and with the edges of the workpiece looking side toside. Once you've got the slotted piece properly positioned, add a couple clamps to hold everything in place.

Attach the slotted top to the two side pieces with #8 x 1 'A" screws - two screws per side. Counterbore the holes for the screws. This is not the lime to split or crack the side pieces. Pull ihe assembly from your vise and remove the workpiece. The fit should be snug so it will lake some muscle 10 remove the workpiece from the jig.

Everything held securely. Once the parts of the jig are positioned around the piece to he mortised, add screws through the top to complete the jig.

You choose the length. The overall length of your mortise is determined by the slot cut into the jig's top. Make sure to compensate for differences between the bushing and router bit.

Plunge a Mortise

Set up your router with 1 he guide bushingand a 2 '/2"-long router bit. You're now ready to work. A bit t his long allows you to plunge a mort ise just over 1 'A" in dept h into the workpiece after passing the jig's '^"-plywood top.

Match thejig'sopeningto the layout lines on your workpiece and clamp the two together in a vise or with other clamps. Zero out the router bit by plunging down (with the power off and the router unplugged) until the bit touches the workpiece, then lock the plunge mechanism. Use the router's depth slop to set the plunge depth.

The base ol ihe router sils securely on top of the jigand the bushing, which filssnugly in the

slot,adds 10 ihe overall stability. To create ihe mortise, release the locked plunge mechanism and pull the router setup light to one of ihe ends. With the bit standing above the work-piece,start the routerand hold lightly against the slot's end as you plunge to full depth.

Allow the router bit 10 retract from the hole, slide the router to the opposite end and plunge a second hole. To remove the material for the balance of the mortise, repeat the plunge action, each lime positioning the router setup over an unexcavated area.

Once mosi of the waste is removed and no section remains that bridges the two sides of your mortise, return to one end of the slot, plunge to the bottom of ihe morliseand make a pass along ihe entire length 10 clean and straighten the sides. Make it a poinl to travel the length while holding the bushing firm to one side, 1 hen make a ret urn pass holding tight to the opposite side. The result might be slightly wider than the 'A" router bit, but because you make the mortise section of the joint first then match the tenon, this won't be an issue.

This jig is easy to build and can be used repeatedly with consistent results. The only decision you'll need to make is should you round your tenons to match the mortise, square the mortise ends lo match the tenons or create tenons with wiggle room-not snug to the mortise's rounded ends. 1 always opt for wiggle room. PW

Clen is a senior editor of this magazine, a published author and the host of the Woodworker's Edge DVD series. Contact him at 531-513-2690 x11293 or glen.huey@fwpubs.com.

Two finishing passes. Once the plunging cuts are completed, finish the mortise with a pass along both faces of the slot. This last step smooths and cleans the slot.

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