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Box Joint Jig

 

 Box joints add a professional touch to your projects, they can be cut on a table saw with a dado blade or with a router in a table with a straight bit. Generally the thickness of the material and the width of the tails are the same, they should be cut slightly deeper then trimmed for a perfectly flush fit.

Instructions To Make

Plan to have a finger that will divide evenly into the height of the box for best results, 1/4", 3/8". 1/2" and 3/4" are common sizes, you will have to make up a jig for each size.

Set up dado head to width and depth required, depth should be slightly deeper than width. Use any 3/4" thick material for backer guide, it should be aprox. 4'' wide and 12" long. Cut the first notch through the backer guide. Note the holes in the miter gauge, they will be used to fasten backer board to it, if yours doesn't have holes drill them now before you proceed.
Cut key stock to fit in the notch, cut enough so that you will have two lengths, one about 3" long the other about 6" long.

Fasten the short key in the notch, move backer guide forward to almost touch dado blade, place second longer key between the short key and the outside edge of tips on dado blade. Clamp the backer board to miter gauge.
Using scrap material wide enough to cut several notches and the same thickness as good material follow directions below and cut two test pieces to check the fit of the joints. If they are too tight or to loose, undo the clamp and move the backer board to compensate. When you are happy with the fit attach backer board to miter gauge with two screws.
To cut the outside tails start by placing material against key for first cut, clamp, cut the first notch, then move material over with the key in last notch cut. Always use the clamp to hold material in position for every cut.
To cut inside tails start by placing outside tail stock notch over the key, then butt inside tail material up to it and clamp to backer board. Remove outside tail stock, make cut and continue cutting notches as above.