Hi Mr. Bird, I'm a hobby woodworker and recently ordered your tambour router bit set. I am building Indiana Hoosier Hutch, and didn't want to used the fabric backed tambours. I tried your tambour bit set, and on my test set, the ball and socket fit very well.
When I ran the pieces for the actual project, and found that the ball socket was pretty loose, allowing the slats to come apart will little force. My theory, and I hope you can confirm this is that I may have shaved a little to close on the shaping of the stock. It seems to me that the fit of the ball and socket is determined by the router bit, and that the socket bit is always the same.
I wonder if I can increase ball size by moving bit "away" from the stock, slightly of course, but hoping that this will increase the ball size for a tighter fit.
Hope this question makes sense.