Thermal Expansion and Diameter Measurement: Why the Steel in Your Tape Matters
Steel grows as it warms. On a 48-inch diameter, a 20°F gap between your tape’s temperature and the temperature it was calibrated at moves the reading by about 0.006″. That’s six times the ±0.001″ accuracy figure Pi Tape® publishes for its tapes, and it comes from the tape alone, before the part moves at all. […]