Tracer Mills

Bob Gaston posted
Fel Bautista I'll bet the tool and die guys were going crazy making the master.

Note the pattern for the curve of a fin on the left and the stylus that comes down to sense it. The diameter of the stylus is the same as the cutting tool. [PolyTechForum] My guess is that, as the boring tool is fed across the material, the stylus would cause an actuator to rotate the material so that the stylus stays adjacent to the pattern's fin. Noting the wires coming from the top of the stylus holders and the two hydraulic actuators in front of the machine, it uses electricity to control hydraulic valves.

Noticing the stylus hanging at the left, I think he has already done a pass with that stylus on top of a model to turn a cylinder into a small radius on the right increasing to the full radius on the left. It is too bad they took this photo after all the fins had been cut. I would have liked to see it in the middle of a pass with only half the fins machined. That would make it much more obvious how the machine worked.

Bob Gaston commented on the above posting
Dennis DeBruler So the left stylus would follow the model on the top surface to control the z dimension while the right stylus would follow the model on the side to control the y dimension? The feed screw would control the x dimension. (Or do I have x and y dimensions reversed?)
[Actually, since these objects are round, the second stylus is controlling the rotation rather than a y dimension.]

Tracer Mills were the state-of-art before CNC (Computer Numerical Control) was developed.
Gary Gotschall I've worked arouind those tracer mills just a little and all I can say is thank God for 5 axis CNC mills...so much better. Progress.

A Google search for "tracer mill" finds several You Tube videos. But they are doing flat objects rather than round objects such as these turbine blades.