Replies

1. 
   Eef | Jan 13, 2010 02:07pm | #1

   hi don,

   are you intending to miter the long edges of a "naturally" cupped board? i would be leery of that. the times i've done this i calculated the blade tilt based on the number of sides i wanted the radius to have. so that a lid with four boards in it would require a 22.5 deg. miter. this may be done at the router table also with a bit of the required angle.

1. 
   DonC | Jan 13, 2010 05:01pm | #2

   Thanks for your reply. No, I want to crosscut a miter on a 14 inch wide board that has intentionally been coopered and glue into a concave shape.

2. 
   flairwoodworks | Jan 13, 2010 05:12pm | #3

   Don,

   I would go concave side down. As long as the concave profiles of the two mating boards are the same, it should not be much more difficult than a regular miter. If you are doing compound miters to get the curves to sit not "flat", then it will be trickier.

3. 
   JeffHeath | Jan 13, 2010 06:08pm | #4

   In addition to what Chris said, you have to make absolutely sure that the coopered board has both edges properly supported by whatever sled you are using to hold the work for mitering. If not, it will rock, and be susceptible to a kickback, which is ..................very bad for your health!

   Be careful, but this is not a big deal if the proper precautions are taken, and you understand the geometry. You should rigidly clamp the coopered board to your sled.

   Jeff

4. 
   hammer1 | Jan 13, 2010 06:31pm | #5

   It wouldn't be any different
   It wouldn't be any different than cutting a hollow back molding, good face/convex up. The work should ride on the "tips", so to speak. I don't think you need a form that fits the the back. If the form isn't a perfect fit, it could throw off the miter. Make a practice cut and see. As long as you are set up accurately for a crosscut miter, the work is adequately supported and won't slip during the cut, you should be fine. I wouldn't clamp down on the coopering. A long wood bar on the miter gauge with sandpaper glued to it should prevent slipping.