Equation for accurate bending (kerfing) of plywood
There have been a growing number of projects out in the 'makeosphere,' where people are cutting slits or kerfs that go almost completely through a thicker piece of wood, allowing it to be easily bent. I am on a super-tight budget, and cannot afford to ruin my $22 sheet of plywood, so I was hoping that someone might be able to help me with some measurements for cutting the kerf-slits in the plywood. Here is the idea all sketched out. I need help with the measurements that are in bold.
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
- 1x | 4 ft. x 2 ft. 3/4 in birch plywood
- 2x | 3 ft. 5/8 in threaded metal rods
- 8x | flat washers
- 4x | standard nuts
- 4x | "end nuts"
- On the sheet of plywood, measure in X inches and mark X number of cross cut lines, X inches apart.
- Measure in 2 inches from each end of the board and draw a line.
- Measure in 2 inches each each side of the board, and draw another line.
- Drill out a 5/8 inch hold at all 4 of these crossed lines.
- Thread a standard nut onto each end of the threaded rod and screw it on 1-2 inches roughly, then slip a flat washer over the threaded rod.
- Bend each end of the board up to create almost 90 degree angles.
- Insert each end of the threaded rod into the holes, slip a flat washer over the threaded rod and screw on each of the four "end nuts."
- Use the standard nuts, and the end nuts to fine tune the bends into 90 degree angles.
- Flip the table over, and enjoy.
Stability is more important to me than curve radius. I don't know if spacing cuts close together for a small curve radius is more or less stable than placing the cuts further apart for a larger radius. I've never done this, but I have seen that there is an equation for this. I haven't been able to find the equation actually expressed, I've just heard that there is one. Does anyone know about this area of woodworking/physics?