Bidspirit auction | Welch Teaching Micrometer

Welch Teaching Micrometer - A large-scale classroom teaching demonstrator micrometer, manufactured by the W.M. Welch Scientific Company. This oversized instrument is designed to illustrate the mechanical principles and scale-reading techniques of a standard micrometer. The device features a heavy C-frame and a stabilizing tripod base, both constructed from cast metal with a hammered grey finish. The word WELCH is cast in raised block letters on both sides of the frame. The measuring spindle is made of aluminum. The thimble and sleeve components consist of a heavy paper or cardboard laminate wrapped around a cylindrical core, bearing printed black scales. The thimble is marked with graduations including the numbers 0, 5, 10, and 20, and features a cross-hatched knurled pattern at the grip end. The sleeve bears a horizontal index line with vertical graduations. A white adhesive label is attached to the base reading Large Welch teaching demonstrator micrometer.