Which route to take for mitered profiles?
When routing a profile on mitered or beveled workpieces, is it better to rout the profile first and then cut the pieces, or vice versa?
—George Wu, Newton, Mass.
Like so many questions in life, George, the answer is: It depends. The size of the pieces, shape of the profile, and overall design of the project all factor into the decision.
In most cases, you get more consistency by first routing the profile on long blanks at the router table, then mitering and attaching each piece individually, making any adjustments to the fit as you go.
For small, delicate workpieces, such as narrow moldings, rout the profile on a wider blank first, then rip the molding from the edge of the blank [Photo A] and miter the pieces to length. The wider blank keeps your hands safely away from the router bit and prevents blowout of the delicate piece.
Some profiles, such as round or bullnose edges, or exceptionally wide or deep moldings, require more than one pass to complete, using the router-table fence as a bearing surface for the workpiece to ride against. Here, you often have little choice but to rout the profile first. The same holds true for moldings impossible to access after assembly, such as the beading around a drawer front, or a decorative molding around a panel.
On the other hand, it sometimes makes sense to rout the profile after cutting and attaching the pieces—for example, when constructing a mitered base or frame around a panel or tabletop. After mitering the pieces and gluing them together, sand the surfaces flush and then rout the profile as the last step [Photo B]. Routing after sanding ensures a uniform profile all the way around the project.
Finally, rout the pieces after cutting and assembly when the profile presents a clamping issue, such as a rounded or thin edge that may crush easily under clamping pressure. Or an odd profile that doesn't allow the clamps to gain a good grip.