Qüïmsgëfääërdën ÏÏ (rëvïsïtëd) Thë Rädïüsïng
A little more progress was made this weekend. I decided on a 12" radius for this board, so I got everything set up and got to work.
I think I'm one of the few here in LC that use radius router bit on my boards. I usually get a number of questions about this procedure, so I'll try to show some good detail about the process. I originally bought these bits from Amazon and they are the SJE brand. I don't think those are available any longer, but Yoniko has them available on Amazon at very reasonable prices.
The first step is to mount the board to a stable and square fixture. (of course I didn't take a before picture, but you can look at the after picture as it is still mounted) The fixture is just 2 layers of plywood that are glued and screwed together and square in all dimensions. I also have a centerline scribed along the long faces for easy alignment when mounting boards.
The fingerboard can be routed with or without slotting the board first, it's up to you. I've had no problems with tearout either way. It goes without saying that the board should be very flat and true before you attempt this.
Next, the bit is mounted in the router table (a table is a necessity, don't do this with a handheld router) and the bearing is removed from the bit. I position the top edge of the cutter at, or just slightly below the centerline of the board. My fixture and board is only on far side of the bit for alignment purposes.
Bring the fence forward and lock one end. Adjust the cutter for a very small depth of cut. Note that because my board is already tapered, only the wide end will get cut on the first couple of passes. The fence will control depth of cut, I do not use the bearing at all.
Hold the fixture with good downward pressure to keep it square to the table and use gentle pressure against the fence. Feed the first edge slowly, then flip the entire fixture end-for-end and feed the other side. Here is the end of the board after the first pass on both sides... just nipping off the corners.
Loosen one end of the fence and move it over a little to reveal more cutter. You can move the straightedge higher on the fence to get a feel for which area of the board will be cut.
After another pass.
And done. I snuck up on this in 4-5 passes, just moving the fence tiny amounts for the last few cuts.
And here is the whole board.
The process usually leaves a small ridge in the center of the board. That will get removed later. I'll glue the board in place, install face dots, thickness the neck, etc. before I true the face of the board.
