Purpose: to check concentricity between two internal diameters or between two external diameters or between one internal and one external diameter.
Description of the fixture: ID to ID concentricity checking fixture is shown in the picture. When bores are adjacent and lack of concentricity is held between close limits this

Purpose: To check squareness of a bore with reference to a face.
Description of the gauge: The construction of this special air plug gauge to measure squareness is similar to that of concentricity checking gauge. Mainly used in cylinder block, bearing cup, engine gears bushing etc.