With this fixture, you can produce perfectly sized mortises with glass-smooth walls and ends. The process is much slower than using a hollow-chisel mortiser, but the results are superior. Use it whenever a joint will be highly visible.

The fixture consists of two parallel tables, one that holds the workpiece and another that guides the paring tool. An adjustment mechanism at the bottom of the fixture raises or lowers the guide table into position where it then locks in place with wing-nut tightened blocks.

The secret to making perfect mortises is in the paring tool. It must have a long primary bevel, be sharp and perfectly flat, perhaps even slightly concave, on the back. I make my tools from square-profiled tool-steel bit stock, which is available from MSC Industrial Supply Co. (151 Sunnyside Blvd., Plainview, N.Y.11803; 800-645-7270) or any well-stocked industrial supply house. The steel comes in several sizes, but I use the 5/16-in.-sq. size the most. Attach a handle to an 8-in. piece of steel, and then grind the steel at a steep bevel, somewhere between 15¡ and 20¡, on the belt sander. This works better than a high-speed abrasive wheel because the belt cuts fast but doesn’t overheat the edge. Now hone a secondary bevel using a honing guide and a progression of Japanese waterstones. Don’t flatten the back of the steel as you do when sharpening a regular chisel. The paring and corner cleanup go better if you just leave the back of the tool alone.

To use the fixture, lay out the mortise with a sharp awl. Hog out most of the waste with a Forstner bit in the drill press. Leave the mortise layout line. If needed, trim out large waste areas of wood with a regular chisel. Now place the workpiece in the fixture, and clamp it in place. Adjust the height of the guide table to the mortise line, and lock the Plexiglas end guides at the ends of the mortise. Keeping the paring tool flat on the guide table, pare the sides of the mortise. Finally, turn the tool 90¡ to trim the end of the mortise.

Bill Webster, Chillicothe, Ill.

Fine Woodworking Magazine, June 1994 No. 106

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