Purfling sounds like a quaint English game involving a grassy field, mallets, and furry animals, but it's actually the strips of veneer that go around the edges of the top and bottom of a violin. The purfling can be plain or quite ornate, bought or made by hand out of veneers of mahogany and pear and maple.
We've opted for plain, store-bought purfling. No matter what pattern or style, the purfling is inlaid into the wood, so a trench about 1.3 mm wide and 2 mm deep needs to be dug all around the top and bottom. The old-fashioned way to do this is with knives to cut the channel, then wee chisels and picks to empty it; a skilled builder like Anya at our workshop can do a single plate in about 2 hours. The simpler way to do it is to use a machine tool such as a Fordham flex-shaft, with a special jig to hold the bit at the proper depth and distance from the edge. At this workshop, I've seen several variations on this, but my favorite is the one made by Tom Croen.
This is the business end of it, upside down from the way it would be used. The cutter head sticks out between two legs; these ride on the top of the board, and set the depth of the channel. The fence is on a threaded post, so it sets the distance of the channel from the edge. The cutter head moves through hard wood like a hot, rapidly spinning knife through butter. It can get a rank amateur like myself through a plate in a matter of minutes.
However, it is a power tool, so it can also get a rank amateur like myself into deep, deep doo-doo in a matter of milliseconds.