How to Cut Finger and Box Joints with a Router or Table Saw Jig
Box joints might not be the most interesting or attractive joints, but they are very sturdy and simple to cut in most shops. Although not as dressy as dovetails, box joints are versatile joints great for all kinds of everyday projects. You can use them to build attractive boxes and trays, good-looking drawers and carcasses, and tool totes and chests strong enough to withstand daily use.
Box joints tend to create very strong joints because of their large surface area, making them perfect for projects like tool trays which carry small but heavy loads. Sometimes confusingly referred to as “finger joints”, box joints are best for joining two frame or carcass members to form a corner. With a series of evenly sized pins and notches spaced along the length of a corner, box joints form simple but attractive exposed connections. They don’t mechanically interlock like dovetails, but box joints do have lots of surface area, so they’re very strong when glued together.
Finger joints are a thinner, more delicate cut than box joints, but work extremely well for long pieces like molding and boats. Finger joints feature a series of fingerlike pins and corresponding tapered notches that interlock to joint two parts together. They’re best used to scarf frame or panel members end to end, to form longer members. Finger joints are very handy for creating parts longer than the stock you have on hand; say, for a crown molding that traverses the entire length of a kitchen or den. Finger-joined scarf joints are also commonly used in boat building; say, for forming the gunwale on a canoe or sailboat.
A sliding fence jig across your router table (or table saw) can help you cut a lot of simple box joints in almost no time. While you could cut box and finger joints by hand, both joints are most quickly and efficiently cut with power tools, in either solid wood or plywood. The easiest methods include using a sliding jig and a table saw, a portable router and a template-style joinery jig, or a router table and sliding fence jig or dedicated box joint router bit. Cutting finger joints requires a special bit used with a hefty router in a router table, or a finger-joint cutter used with a shaper.