Mortising

This is the job for which the fixture was designed.Tackling this operation will expose you to all the workings of the fix-O tunc. You have to adjust all three axes of movement (discussed at the beginning of this chapter). You have to work the tabletop grid and set toggle clamps. You have to do the mortising dance.

O 1- Lay out the mortise. This is where it begins. On J5 a piece of the working stock, pencil off the mortise you want, where you want it. Will it follow the Rule of Thirds, having a width equal to one-third the stock's thickness? Will it be centered across the stock thickness? How long will it be? How deep? Your layout should answer the first three questions. The answer to the fourth question will be I revealed in setting up the router.

2. Set up the router. This is a slot mortiser, cutting mortises in back and forth passes at a given level.Thus, the width of the mortise dictates the diameter of the bit to use.

The conventional wisdom is that spiral upcut bits are best for mortising, and that's true. But you need not feel that's the only style of bit you can use. I've used straight bits of every style—straight flue, shear flue, single and double flute.

Equally important as the diameter is the length of the bit.To the desired mortise depth you must add Vz inch for the thickness of the mounting board, maybe % inch of space between the mounting board and the collet nut.aiw at least 1/j inch of shank to be gripped by the collet. So the bit needs to be at minimum 1 '/a inches longer than the mortise depth.

Given these guidelines, choose your bit for the nioni.se and tighten it into the collet.

Now set the plunge router's depth stop for die mortise depth. To do litis, you merely have to plunge the router-without the springs, it will stay plunged as far as you pud) it—and measure the portion of the bit extending from the mounting board. Plunge the router until the correct amount of bit is exposed, then set the depth stop at that point.Thca pull the router back, retracting the bit (though not fullj)jj and ready the machine for the next setup step.

3. Adjust the mounting board height. Set the stoci with the mortise laid out on it beside the bit. Ixxwcn the three knobs securing the mounting Ixxird and make a coarse setting, raising or lowering the bit as close as posstfj between the layout lincs.Tighten at least one knob to hold the setting, and spin the check nuts up against the slotted plate

Setting the mounting board height can be done with considerable precision, thanks to the number of threads per inch (16) on the adjustment rod and the style of the check nut. With the workpiece beside the bit. turn the nut to raise or lower the bit so it aligns with the layout lines, as shown. The nut (inset) has four holes, allowing you to easily "dial" a quarter- or half-turn for very fine adjustment.

Examine the level of the bit against the mortise layout dosdy. If it seems appropriate, loosen the knob(s) and turn the cheek nut to raise or lower the bit. When you are comfortable with the setting, tighten all three knobs, and jam the second check nut against the first.

4. Set the lateral-travel limits. This can be done using the laid-out mortise or the grid on the worktop, whichever is easier for you.

Setting the stops for the mortise length is easy to do using the grid on the bench top. Pick out the grid lines that represent die extremities of the mortise. With the bit plunged, look down on the grid and align the bit's left edge with the line representing the mortise's left end. Set the sop on the adjustment rod's left to prevent the router from moving any farther in that direction. Slide the router to the right, aligning the bit's right edge with the line representing the mortise's right end. Set the right stop.

5. Position the work. The fixture has been set to create a cut of a specific length.The tasks now are to place the workpiece so the mortise will be where you want it. and to position a toggle clamp to lock the workpiece down during the muting operation.

Positioning the workpiece is a matter of aligning the monlse layout lines with the appmpriate grid lines. For a production run, it saves time if you clamp a stop block to locate the workpieccs automatically. The stop can be clamped with a C-clamp or with a toggle clamp.

The toggle clamp designated to hold the workpiece

Setting the stops for the mortise length is done easily using the bench-top grid. Look down on the grid, and align the bit with grid lines that represent the ends of the mortise. With the bit at one mortise-end position, spin the check nut on that side until it seats against the chassis side. Move the bit to the other position, and set the stop on that side.

should be positioned so that its spindle applies pressure to die work as close to the mortise as possible.

6. Rout a test mortise. With everything set, lock down the test piece and rout the mortise. Then examine and evaluate the mortise. Measure it. Do any adjustments need to be made? Is it centered in the edge? Is it the correct length?'Hie correct depth?

If necessary, adjust the settings.

7. Rout the work. When all is right, gel to work on the good stock.

A word or two about technique is in order here. I grasp the router's knobs, one in each hand, but I set my thumbs against the router mounting board.You'll probably find, as I did. that you have smoother control of the plunge action if you apply pressure with your body rather than with your hands.Thc thumbs set against the mounting board counter this pressure, controlling the rate and depth of plunge. With spiral upcut bits, it seems easier to plunge and cut laterally in one continuous motion, radicr than plunging first and then cutting Literally. Just be sure you don't force a bit, especially a solid carbide one.

End mortises are easy to rout with the slot mor-tiser. Turn the workpiece so its enc confronts the bit. rather than its side. Though a single toggle clamp will hold the workpiece in place while the mortise is routed, a stop block locates it for the cut automatically.

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