Knife-edge /(?)/

Knife·-edge

Knife-edge

n.
  1. A piece of steel sharpened to an acute edge or angle, and resting on a smooth surface, serving as the axis of motion of a pendulum, scale beam, or other piece required to oscillate with the least possible friction. (Mech.)

Phrases & Compounds
Knife-edge file
See Illust. of File.