At first glance, the Butterfly Spline Bit seems like a very simple and limited use tool. But look closer and you can find a lot of useful applications for these splines. The bit cuts a butterfly profile, essentially two dovetail keys joined at the smaller width.

I used to teach router table classes and the most popular part was, hands down, making cabinet doors. Virtually every bit manufacturer offers door making bits in several profiles. These come in a set, where the mating profiles are two separate bits, and a single bit form, where both cuts are contained in one bit. The bit I'm using is the single cutter type.

The Multi Profile Bit is the first in a series that will cover router bits made to help you perform difficult router tasks more easily, the proper ways to set up & use them, and tips for getting the best results.

Many manufacturers make sash bits, but most are designed as 'stub' tenon bits, working more like a stile and rail door set. The Freud set is designed to make long tenons in the joint connections, making a vastly stronger window. Because of this, the bits require a bit more work, but the extra effort is well worth it.

There are many projects that require the milling of pockets. Antique game tables nearly always had dished-out areas for candles and game chips. Signmakers often raise letters by removing the background around them, and all sorts of serving trays, bowls and stands are dished out to provide a rim for keeping things in.

Gluing boards together to form larger panels is something of a mystery to novice woodworkers. Boards don't line up properly, and clamps can tend to force the edges out of alignment. Boards may have a slight bow along their length and just try to get a clamp into the middle of your panel to fix it. There is a wide array of joining systems out there to help, but my personal favorite is still the Glue Joint router bit.