How to rout matching curves in two mating boards

[Russ Kupiec]

In a nutshell, if one is trying to join(glue and clamp) two boards together that meet along a curve, one cannot use the same pattern board board for both sides of the curve because the radii would not match. Somewhere I know I saw a write up about how to do this. Namely, cutting a curve in one long board that matches a curve in the mating board whence you join them together. As my age compromised brain recall, the method had something to do with cutting a pattern for the first curve and then using that pattern board to cut another pattern board to be used for the second mating board. Does this ring a bell with anyone?
Any help would be appreciated.
Thanks in advance
Russ

[pat warner]

A pictograph (http://patwarner.com/images/templates_cover_shot.jpg)to get you started.

[Alan Schaffter]

You want an easy way to make two boards with curved edges that will mate precisely and glue up with no gaps?

With slight modification you can use this technique whether you are cutting your own curve or matching one. It doesn't even require that the curve be cut carefully and no measuring is required.

1. Use a piece of MDF or hardboard to make two templates that can be used with a flush trim or pattern bit.
2. Trace an existing curve or draw you own down the middle of the MDF, then use a bandsaw, jig saw, scroll saw, coping saw, etc. to cut along the line- KEEP TO ONE SIDE OF THE LINE.
3. Clean one template up to the line with files, spindle sander, sandpaper, etc.
4. Seal or size the smoothed edge (shellac, white glue, etc.).
5. When the sealer is dry, apply thin packing or cellophane tape to the edge.
6. Mix up some body filler (Bondo) and apply it to the still rough edge of the other template
7. Clamp both templates together and clean up any Bondo squeeze out.
8. When the Bondo is hard separate the templates, clean up any remaining squeeze out, and remove the tape.

You now have two templates that will nest perfectly. Use them with a flush trim or pattern router bit to make pieces that will also mate perfectly. Depending on the tape used there will be a tiny gap left for glue.

http://www.popularwoodworking.com/wp-content/uploads/Opener-225x300.jpg

[Chris Parks]

It is not a router but have a look at the bandsaw jig in this link as it does just what you want

http://www.frontlineengineering.com.au/

[Larry Edgerton]

I use Alan's method with one exception. I use West System on the bearing surface of the patterns as it makes the running surface of the pattern to be very hard and used for as many times as necessary without developing bearing tracks.

Larry

[Alan Schaffter]

I use Alan's method with one exception. I use West System on the bearing surface of the patterns as it makes the running surface of the pattern to be very hard and used for as many times as necessary without developing bearing tracks.

Larry

Epoxy is probably much better for longer wearing template edges. MDF edges aren't very hard and can deform and wear quite easily. By the way I used that technique for making perfect cutouts for router table inserts- and also had my tip about it published in WW Journal.

Another note- the picture of the cutting board in my previous post was taken from a short FWW article- Steve Shaunesy carefully cut the bandsaw curves and glued everything back together with no filing or sanding. He said it worked fine and the edges mated tightly. I'm a bit skeptical and doubt I would be as successful with my bandsawing skills.