Tre-pan′.
1. (Surgical.) A crown saw used principally in removing portions of the skull. The trephine is an improved form. See trephine. One boring instrument of the Romans was the trypanon, whence our name trepan. Whether it was really a crownsaw does not clearly appear.
2. (French.) A workman's name for the steel at the foot of a boring rod. Trepang. A trepan in the Belgian section of Machinery Hall, Centennial Exhibition, Philadelphia, 1876, was 10 feet in length of face, and weighed 10 tons. It was rotated 6 inches after each stroke, and dug a hole 10 feet in diameter. Sand buckets and claws removed the mud and large stones from time to time; the instrument being intended to work in water and dispense with a caisson. A second reamer, 15 feet face and weighing 15 tons, followed the former to enlarge the hole, which was then tubed with cast-iron sections.
