Requirements for casting square boxes: Each working surface of the square box must not have rust, scratches, cracks, dents, or other defects that affect the metrological performance. Non working surfaces should be sandblasted and painted, with chamfered edges. There should be signs on the inner wall of the square box, indicating specifications, dimensions, grade, factory number, and manufacturer name.

Casting box accuracy: For scraping boxes, in addition to checking the flatness, the contact spots should also be checked using the coloring method. The number of spots in any square with a side length of 25mm is: no less than 25 points for level 1 and level 2; Level 3 should not be less than 20 points.

Method for testing casting square boxes: For square boxes with a side length of 315mm or less, 1mm measuring blocks are placed at each end of the tested surface of the square box during testing. A straight edge with a cutting edge is placed on the working surface of the measuring block, and then a measuring block is used to test the plug at each tested point. The difference between the size of the measuring block group just inserted and the size of the measuring blocks at both ends is the deviation between the two ends of the tested point. This verification should also be conducted on several sections of the square box working face in the longitudinal, transverse, and diagonal directions. When the error directions of the straight lines measured at various positions are consistent, take the maximum value. When the error directions are not consistent, take the sum of the large positive and negative differences, which is the flatness of the inspected surface plane.

Casting square box purpose: mainly used for checking and marking the parallelism, perpendicularity, etc. of components.

A cast square box is a concrete hollow cube made of cast iron or steel with six working faces, one of which has a V-shaped groove.