Popular Woodworking 2001-06 № 122, страница 15
Ingenious Jigs Microadjustable Finger Joint Jig What a difference a machine screw makes. You find them lurking in bins in hardware stores, hanging out in plastic bags in home centers, rusting in baby food jars in garages and basements all across America: flathead machine screws with 32 threads per inch. Few of us ever suspect that these unpretentious bits of hardware could be so incredibly helpful, particularly to those of us who still use the ancient and venerable English system of measurements. These tiny bolts are a cure for many troubles that afflict our accuracy. They can eliminate the error from a trial-and-error method and turn a homemade jig into precision equipment. Consider the traditional finger joint jig. It's designed to make evenly spaced square notches in the ends of adjoining boards, leaving multiple tenons that interlock to form a finger joint. The standard finger joint jig has just three parts: a back that you attach to your miter gauge, a movable face that feeds the wood into a dado blade to cut the notches, and a tenon that aligns the wood for each cut. To set up this jig, you must move the face right or left, adjusting the space between the tenon and the dado blade, so the fingers will be properly spaced. If the fingers are too close to 5/32" diameter holes with 5/16" diameter countersink 1/2" 2 3" 1/2" gether, the joint will be loose. If too far apart and they will be too tight to assemble easily. Positioning the face properly is often a frustrating loop of trials and errors. Cut a finger joint, test the fit, move the face, cut another joint, and so on. But if you add one more part to this jig — a small wooden block that mounts a #10-32 machine screw and serves as an adjustable stop — you can escape this frustration. Because the machine screw has 32 threads per inch, one turn will move it precisely 1/32", one half turn moves it 1/64"; one quarter turn, 1/l28". When the flat head is resting against the face, the face will move a precise amount. No guesswork! continued on page lb 3/8" wide x 3/4" long slots by Nick Engler Nick is a contributing editor to Popular Woodworking, the author of 52 books on woodworking, and a builder of pioneer airplanes. #10-32 x 2" flat head machine screw, knob and stop nut #8 x 1 1/4" long flat head wood screw (2 required) 3/8" diameter with 1" diameter x 1/4" deep counterbore 3/8" x 1 3/4" long carriage bolt, flat washer, and wing nut (2 sets required) 24 Popular Woodworking June 2001 |
