One of the tricks I keep up my sleeve to create flush surfaces and tight-fitting assemblies is to start with parts that are slightly oversized. Then, after assembly, I trim the parts smooth and flush.
A good example of this is Martini table from Woodsmith no. 264. The central medallion in the tabletop is inlaid in the surrounding veneer so that it’s slightly proud of the surface.
The catch is you need a method for trimming parts smooth and flush that’s quick and reliable. For that, I often turn to my routerand a specialized jig.
Simple Jig. The reason for the jig is shown in the drawing. A standard baseplate will catch on any protruding edging. The stepped design of this jig solves that problem. A portion of the base is elevated to provide clearance to trim excess material. While I made this jig to fit a compact router, you could easily make one to accommodate a standard-size model.
In the exploded view drawing, you can see the details for the jig, but I want to point out a few highlights. First, I used Plexiglas for the main part of the base. This increases the amount of light and visibility around the bit during use. (Using 1⁄2" plywood will work, too.)
The second thing is that the base is considerably larger than the stock router baseplate. This extra size gives the router a more stable stance in use.
Finally, I included a reversible stop on one end. When trimming along an edge, the stop acts like an edge guide to limit the travel of the bit. For trimming tasks away from the edge, you simply flip the stop over and it provides support so the router won’t tip.
Straight Bit. You can get good results with almost any kind of straight bit. But I’ve found that bits like the one shown in the right margin, with flutes running straight across the end, “plane” the surface and leave it much flatter. Some types of straight bits have a V-shaped end that may leave swirl marks on the workpiece.
The Setup. It only takes a little work to get the bit and jig ready for use. First, you need to adjust the depth of the router bit.
Ideally, you want the bit perfectly flush with the surface of the bottom of the jig. A small straightedge is a great tool for getting you in the ballpark. But it’s always a good idea to do a quick test cut.
Next, I set the stop at the end of the baseplate. It’s positioned so the inside edge of the bit is flush with the edge of the plywood panel.
The Technique. Once the bit and baseplates are set up, you’re ready to start routing. There are a few things to keep in mind. The main thing is to apply firm pressure on the handle. This prevents the router from tipping and spoiling the cut.
Unless the edging is thin, I like to remove the waste in several light passes. Finally, rout in the opposite direction (right to left) to get a clean cut and prevent the edging from tearing out on the exposed front face.
This setup can be used for more than just trimming edging. The drawings show a couple other examples. The small amount of effort spent in making the baseplate will pay off with smooth surfaces and perfect-fitting assemblies.