01-03-2013, 09:43 AM
A few days later...
I've been staring at that old picture of the planer/shaper attachment and it finally hit me - the path that the follower travels isn't parallel to the axis of the work. As the follower travels up the inclined rod, the distance between the work and the rod changes. It's actually following a curve rather than a straight line, and generates a poor helix. In contrast, the rifling machine is indeed a straight line with the path imparted to the work via rack and pinion gearing, generating a true helix.
I've been staring at that old picture of the planer/shaper attachment and it finally hit me - the path that the follower travels isn't parallel to the axis of the work. As the follower travels up the inclined rod, the distance between the work and the rod changes. It's actually following a curve rather than a straight line, and generates a poor helix. In contrast, the rifling machine is indeed a straight line with the path imparted to the work via rack and pinion gearing, generating a true helix.