Mechanical counterweight blocks are mainly used for the inspection of parallelism and perpendicularity of components, as well as for supporting workpieces during marking. They are generally cube or rectangular prisms with equal side lengths. Various specifications and equal-height boxes and rectangular cylinders can be produced according to user requirements. 

Usage: The square box is mainly used for the inspection and marking of the parallelism and perpendicularity of components. The square box is a hollow cube made of cast iron with exactly six working surfaces, and one of the working surfaces has a V-shaped groove. The environmental conditions for the square box inspection: normal temperature and normal humidity. 

Accuracy: For the scraping development box, in addition to checking the flatness, the contact spots should also be checked using the coloring method. Within any square with a side length of 25mm, the number of spots for grade 1 is 1 point; for grades 2 and 3, it should be no less than 25 points for grade 2 and no less than 20 points for grade 3. 

The working surfaces of the box should be free from rust, scratches, cracks, depressions and any other defects that may affect the measurement performance. The non-working surfaces should be sanded, painted, and the edges should be chamfered. There should be a label on the inner wall of the box, indicating the specifications, dimensions, grade, factory serial number and manufacturer's name. 

This inspection should also be carried out on several sections in the longitudinal, transverse and diagonal directions of the box working surface. When the direction of the straight line error at each measured position is consistent, take the maximum value; when the error directions are not consistent, take the sum of the maximum positive difference and the maximum negative difference as the value; this is the plane degree of the inspected surface. The mechanical counterweight block is manufactured in accordance with the JB/T3411.56-99 standard, using material HT200.