Plain Mechanics Protractor

A flat, steel plate of rectangular, square or semicircular shape, graduated in degrees. A pivoted arm is attached to the plate by means of a stationary bolt and thumb nut which locks the arm in any desired position. Used primarily in the metal working trades for laying out and transferring angles, scribing lines, and checking clearances on end mills and the like. Excludes protractor, one arm; protractor, two arm; protractor, three arm.