Routing grooves in curved drawers, part 2
I’ve blogged about how to cut grooves for drawer bottoms in curved drawer fronts (in Part 1). One thing I didn’t point out then is why you need a fence to do this. There are slot cutting bits out there that can cut shallow and narrow grooves like the ones needed and you could use that bit by itself. However, you shouldn’t. Not only would that leave the entire cutting head exposed, it would also require you to balance the drawer front on its edge without any additional support. That’s a recipe for disaster. The edge is just too narrow to rely upon. So, you need a fence. The fence I showed in my previous post works great for radius curves (ones that can be drawn with a compass or cut with a router on a trammel), but not for non-radius curves.
The problem with non-radius curves is that some parts of the curve have a tighter radius than other parts and if you make a fence that has the exact shape of the curve there will be parts of the drawer front that won’t contact the slot cutting bit as you push the front along the fence. The solution is to make a fence that has a radius that is tighter than the smallest radius on the drawer front. Take a look at the photos to see how I did that.
Also, there is a photo that shows how I cut individual drawer fronts from a larger curved blank. I use this technique when there is two or more drawer fronts in a row. I laminate a single blank and then cut the separate fronts from it. The angle cut on the ends is exactly correct and the fronts fit into their openings without adjustment.
The problem. The radius on this drawer front blank (there are actually two drawer fronts in it) changes along its length. How do you safely rout the groove for a bottom on its back?
The solution. Make a fence with a radius that is smaller than the smaller radius on the drawer front. I did this by drawing a arc on a piece of plywood and running the drawer front around it. What you want it to be able to always keep the inside face on the same point of the arc as you feed it past that point.
Make room for the bit. I drilled a big hole--the diameter on this one is over 3 in.--to accomodate the bit. I did not drill all the way through, so that the bit would not be exposed from above.
Push the cutter through the fence. A straightedge clamped to the router table works as a fence for the fence as I push it back into the bit. You need to stop and check how far the cutters stick out past the fence. My groove was 1/8 in. deep.
Clamp down the fence. Do it before removing the straight edge so that you don't need to worry about it moving out of alignment.
Use a feather board. This one isn't feathered, but you get the idea. It ensures that the entire lenght of the drawer is cut by the bit at the same point along the fence, which means that it's the same depth throughout.
It makes the tight curves. This is the one you need to worry about.
How to cut the individual fronts from the blank. Use a fence shaped to curve of the drawer front blank Line up where it needs to be cut with the blade and clamp it to your miter gauge. The angles cut are precisely what they need to be.