This is angry_monk's dial calipers.
Taken from his "in pieces" .stl files, split apart as needed, and recombined into a single-plate file suitable for output to a regular FDM printer.
All pieces have been resized for metric measurement, 3cm gradation, and rotated to printer-friendly orientation.
If printing with ABS, you must have a fan pointing at the extrusion target. In my case, that consisted of a fan shroud/duct [ http://www.thingiverse.com/thing:989420 ], fastened around my extruder's cold end heat sink.
- Hot end temperature: 235°C
- Bed temperature: 110°C
Some minor sanding of surfaces and slight reaming out of a couple of holes is about all I needed to do to fit everything together, and a few drops of superglue to make it permanent.
However, despite adding a little bit of light grease, the gear ratio between the rack and the final drive gear on the needle is too high to allow for the overall "slop" between the gears.
The calipers can only safely be opened/closed by either rotating the big gear left of the dial (which will cause the needle to skip teeth), or spinning the needle. It is possible to take a precision measurement by spinning the needle to open/close it.
All resizing and plating done in Slic3r. Black marks expertly added and needle "painted" with a sharpie. ;-)