"an Adjustable Point Caliper" -in various metals
The design and fabrication of this little tool was driven by the need to reliably lay out the surface of lathe turned spheres.
I cut off and did some minor machining on the tips of a drafting compass. I also reworked the tips of a thickness caliper which required some minor welding, grinding, drilling, and finally two tapped holes to receive the drafting tips.
The final result allows for the adjustability of the working ends, enabling them to always point into the center of various diameters of spheres. This keeps the tips anchored properly, eliminating slippage while laying out upon the surface.