Measuring diameters simply and accurately

Exotic, high-tech devices might be all the rage, but a simple, uncomplicated tool called Pi Tape (Pi Tape Corp., Escondido, Calif. pitape.com), has been providing accurate and uncomplicated diameter readings for round and out-of-round forms in a variety of industries for over 60 years. Simply wrap the tape around the object being measured, apply some tension, and read off the diameter to within 0.001 in. for objects with diameters up to 144 in. (Metric tapes measure objects with diameters up to 3,600 mm with a tolerance of 0.03 mm) Tapes consist of 1095 spring steel. Numerals are engraved and acid etched on a ground surface. In terms of speed, the tapes are much faster than using calipers or micrometers. And while a caliper that measures 60-in. diameters to within 0.003 in. costs about $1,600, a Pi Tape for the same job costs less than $90 and is accurate to within 0.001 in. The company makes tapes for inside and outside diameters, and also for measuring O-rings.