Woodworker's Journal winter-2010, страница 31
Box joint jigs depend on an indexing key to set the pin and slot spacing.
You can purchase a box joint jig from woodworking suppliers such as Rockier or make your own simple scrap jig and fasten it to a miter gauge.
tern. For this overview, we'll use Rockler's Box Joint Jig, which mounts in the miter slot of a router table, to demonstrate the task.
Setting Up the Jig
Rockler's jig comes with three aluminum indexing keys, in 1/4"-, 3/8"- and 1/2" sizes. They're interchangeable on the jig and fit into a dado. Here, we're mounting the 3/8" key to match a 3/8M-diameter spiral upcut bit that we'll use to cut the joint slots (see top right photo). If you build a miter gauge-style jig instead, make the wooden key's thickness exactly match your bit's diameter and long enough to pass through the scrap fence and your workpieces.
The next step is to install your router bit and raise it until it's slightly proud of your workpiece thickness (see bottom left photo). This way, the pins will protrude a tad in the finished joint so you can sand them flush. Since workpieces rest on a base on Rockler's jig, the bit height
must account for the base's thickness, too.
Now adjust your jig so the distance between the edge of the bit and the indexing key matches the bit's diameter. This way, the space between them establishes the pin width. In the bottom right photo, we're using a 3/8" x 3/8" brass setup bar to set the gap precisely. It's crucial to make this adjustment carefully so your pins and slots are neither
Adjust the bit height until it is a tad proud of the workpiece's top face.
too loose nor too tight. Tighten the jig base in the miter slot — or fasten your shop-made jig to your miter gauge with screws — to lock the setting.
Size and Label Workpieces
Next, cut your box joint parts to size. Typically, box joints are laid out so the edges of each joint end in full pins on one of the two workpieces. So, as you determine the width of your parts, count out
Set the gap between the bit and index key to exactly match the bit's diameter.