Maybe I don't understand what "spherical teeth" means.JamesTSG wrote: [spherical teeth] have an undefined (but small) contact surface and engagement angle. Conventional gearsets have a fixed angle relationship. Deviate by even a small amount from that and bad things happen (uneven wear which induces slop, hooking, broken teeth, etc.). You would not use them on anything but a CV type joint/pivot.
I had mused on the idea of hinging involute bevel gears, and you can generate a tooth profile (as such) that uses sections of a cone of action that's centered on the axis of the hinge. Then you can get circular contact "lines" over some range of angles though the self-overlapping nature of the double cone imposes some limits, and there's still a single point of contact at the focus. The tooth profiles I generated with those assumptions don't look spherical at all, and you sacrifice the offset insensitivity that straight involute gears enjoy.