This is a Yellow Level Tool and is unlocked by Metal Shop Orientation

This instrument is the main squareness reference for the shop. The cylinder has been ground to be very precisely round, and the ends have been ground perfectly perpendicular to the sides.

• It is typically used on the Surface Plate, in conjunction with a Surface Gauge, a Dial Test Indicator(DTI), and a “bumper”.
• The “bumper”, in our case, is a bearing race that is laid flat on the surface plate, and placed in the “V” of the surface gauge.
• The DTI is aligned with the centerline of the bumper.
• The bumper, held in the “V” of the surface gauge, is put in contact with the cylinder square.
• The surface gauge is rotated back and forth against the cylinder square, and the DTI is adjusted until the probe tip touches the cylinder, and reads Zero at the highest point of the arc.
• The surface gauge is now calibrated to square. The cylinder square is moved aside, and replaced by the part to be queried.
• The surface gauge is rotated back and forth against the part. If the DTI reads Zero at the highest point of the arc, the part is perfectly square!