Starrett 81970 3 Face Granite Tri-Square For Granite Surface Plate, Grade A Inspection, 6" Base, 9" Height, 3" Thickness

Three-face granite tri-squares provide an excellent, economical way for accurately checking the X-Y-Z axes on CNC machine tools and coordinate measuring machines. Lying in the horizontal position, with an indicator in the spindle, the X and Y axes can be checked for 90 degree squareness. With the square in the vertical position, tracing along the vertical edge of the square can check the perpendicularity of the Z axis. Granite tri-squares may also be used in the same manner that steel squares would be used for the direct checking of squareness and straightness.