Quote Originally Posted by stephanb View Post
FYI I've been looking to make an adapter to allow my D1-4 chucks to be mounted on a rotary table. One of the first thing I noticed was that 7 1/8 degree taper. I suppose it is well know by all here, but I found that tan(7 1/8 deg) ~ 1/8 which greatly simplifies the necessary calculations.
Most odd angle tapers come about because they are designed to a certain slope. In this case 1 in 8 probably. I suspect that the design intent was 1 in 8 and that the angle follows from that.