Here are plans for a simple caliper, handy to have around the shop for measuring thickness and diameters. Anytime I can build something that helps me build something else I am always pleased.
The plans should be as accurate as your cutter or printer is, I actually used this project as a collaboration for my laser.
For updates on my other projects and things check out: 4volt.com/blog/
If you don't have a laser you can print the PDF and glue the paper down to any flat material and cut it by hand.
In the case of a laser, I engraved the markings and painted them, then sanded off the extra paint.
After the paint is dried and sanded, assembly is simple. The lower caliper arm is bolted to the other sliding parts with 4- m3 bolts. The lower caliper arm has a few millimeters of adjustment space so you can change how tight the slide is.