Application and verification method of cast iron square box

The use of cast iron square box: It is mainly used for inspection and marking of the parallelism and verticality of parts and components. The square box is a cavity cube of six concrete working surfaces made of cast iron or steel, one of which has a V-shaped groove.

Cast iron square box requirements: square box on the working surface can not have rust, scratches, cracks, dents and other defects that affect the measurement performance. Non-working surface should be sand paint, edge chamfering. There should be a sign on the inner wall of the square box, and it should be marked with the specification size, the level factory number, and the name of the manufacturer.

Accuracy of square cast iron box: In addition to the flatness of the square box, the contact spot must be checked by coloring method. The number of spots in any square with a side length of 25mm is: Level 1, Level 2 is not less than 25 points; Level 3 is not less than 20 points.

The test method for cast iron square box: For the square box with the side length of 315mm and below, a 1mm measuring block is placed on both ends of the tested side of the square box and the knife-edge ruler is placed on the working surface of the measuring block. The plugs are tested at each of their inspected points. The difference between the size of the equivalent block group just inserted and the size of the two ends of the block is the deviation between the pair of tested points. This verification should also be carried out on several sections of the face, sides and diagonals of the face of the square box. When the direction of error is the same in each straight line of the measured position, the maximum value is taken. When the direction of error is inconsistent, the sum of the maximum positive difference and the maximum negative difference is taken as the flatness of the plane of the examined surface.