This article was originally published with the title “How to Measure Closely with Ordinary Calipers” in Scientific American Magazine Vol. 108 No. 22 (May 1913), p. 495 doi:10.1038 ...

The calipers are easy to use, inexpensive and portable, but results often depend on the skill of the technician doing the measuring. Accuracy is with 2 to 4 percent, again depending on the skill ...