Rareearth Magnets

The magnets we played with as kids are quite a bit different from the small, super-powerful magnets used to make this vise. The new versions are called "rare-earth" magnets because of the rare-earth elements—samarium and neodymium—used in [heir manufacture. The magnet-making process starts by compacting a finely milled powder in an electromagnetic alignment field. Then the material is sintered and heat treated to achieve full density and optimize magnetic properties. Final shaping of the magnet is ^^^^^^^ done by grinding with diamond abrasives.

Unlike conventional magnets, the rare-earth fa^,^^ versions are very resistant to being demagnetized. ^^■HP P^V | And they become even stronger when backed H^^ ^L ^ t up with iron or steel. These high-tech magnets flk \ 1 have helped manufacturers pack more power into V increasingly compact cordless tools. But creative cabinetmakers have also found ways to use them in their work. (See page 54.) You can buy the magnets from fee Valley Tools (800-871-87 58). One note of caution: Take extra care when handling rare-earth magnets; they're very brittle and will break easily.

Powerful mini-magnets.

These rare-earth magnets have enough pulling and repelling power to operate the ratchet action of the vise.

Cut the notch shoulders on the table-saw, with tlie blade raised V4 in. above the table and set for a 7° bevel. After culling all the shoulders, mark the ramp, or long, angled cuts. Take care to leave a '/¿-in.-wide land, or flat, area next to each shoulder cut. (See Fig. 2.) Cut the ramps on the bandsaw. Each cut will create a slim triangle of waste. Clean up the notches with chisels and files, followed by 120-grit sandpaper.

Note: If you're making several vises, you might want to build a router jig for notching the stem, like 1 did. My jig is basically an open-ended wooden box (like the slide box) that the stem blank can be clamped in. The router base rides on a 7° platform built into one side of the box, making it easy to rout ramps that are smooth and precise.

Making the Head

The head of the vise needs two holes—-one square (for the stem) and one round (for the screw). Lay out these Openings as shown in Fig. 2, then cut the square through mortise to match the cross-section of the stem. For the Screw hole, follow the directions that came with your threading tools. Wood threaders are available from Woodcraft Supply (800-225-1153) and from The Beail Tool Company {800-331-4718). My threader requires a 1 Vg-in.-dia. hole for a 1 l/2-tn. tap.

Lay out the arc at the top of the head, then cut it and sand it smooth. Glue the stem into the head and pin it with a pair ol -/y-in.-dia. pegs. As shown in Fig, ], each peg should extend through the stem and the full width of the head.

Turned Parts

The screw, hub, and handle are made from turned parts. To make the screw, turn a 1 Uj-in.-dia., 5 l/ij-in,-long cylinder. Cut threads to within 1 '/§ in, of one end. The unthreaded end gets glued into a hole in the hub blank, which you can cut roughly larger than its finished dimensions. After gluing the screw and hub assemhly together, mount it on your lathe and turn the hub to its finished size. Before taking the assembly off the lathe, round the end of the screw slightly. This will help the vise to clamp tightly on pieces that are not evenly shaped.

Set up the hub in a V-block holder on your drill press, and bore a centered, -Kj-in.-dia. hole for the handle all the way through the hub. The handle diameter should be about 'Vjf, in, so that it can move freely in its hole. Finish up this part of the project by installing O-rings and end caps as indicated in Fig. 1. These rubber rings do a good job of absorbing t he shock of the handle slipping back and forth in its hole. You'll find a selection of O-rings at most hardware stores.

The Slide Box

The slide box does just what its name implies: It provides a square channel for the vise stem, allowing it to slide ¡n and out, and to lock in place. The slide box mounts to the underside of the workbench by means of lag screws or bolts that extend through four ^/g-in.-dia. holes. (See drawings.) When mounting the finished vise, you may need to shim it to get the top of the vise head level with the top of the bench.

The parts of the slide box are easy to make and assemble. Side, bottom, and top pieces can be joined together with glue and screws. When assembling the box, take care wirh its interior dimensions. The stem needs to slide smoothly inside the box, but with a minimum of play. 1 recommend adding '-'¿4 in. to the finished cross-section of the stem to arrive at the interior dimensions of the box. Try this trick for a good fit: Build the box right around the stem using business cards as spacers.

When fitting the two bottom pieces, leave a 2'/g-in. gap for the dog. Be sure to cut an 83° angle on the back end of the front bottom piece, as shown in Fig. 2. This drawing also shows the size and shape of the dog and the location of the magnet set into its bottom side. Note that the dog is about !/g in. shorter than the opening in the bottom of the box, and that the edges farthest from the magnet are slightly rounded. This promotes easier movement.

Installing the Magnets

The three magnets are identical l/2-in.-dia., '/¡¡-in.-thick discs, available from Lee Valley Tools (800-871-8158). They should be glued into predrilled holes so that the top of each magnet is just below the wood surface. Hole locations are shown in Fig. 2. Make sure that you glue the two magnets in the lever with their polarity reversed. 1 used epoxy adhesive; cyanoacryl.ue will also work.

Attach the release lever to the bottom ot the box with a flat-head wood screw. Tighten the screw so that the lever can pivot easily. To limit the lever's throw, glue two l-ij-in. dowels into the bottom of the slide box.

Notch the sacrificial jaw to fit loosely over the stem so it can twist to accommodate slightly nonparallel work. I recommend an oil finish for all vise surfaces. This promotes dimensional stability of the parts and keeps sliding smooth. A

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