Dimensional deviation or the permissible tendency to exceed the standard. The "size" here mainly refers to the outer diameter and wall thickness of steel pipe. Usually, some people call the habit of oversize size "out of tolerance", which is not strict in equating inclination with tolerance, and should be called "out of tolerance". The tendency here may be "positive" or "negative". Very few of the steel tubes in the same batch show the phenomenon of "positive" and "negative" tendencies.
The dimension of the product outline is beyond the tolerance range of the product standard rules. It is a quality defect of metal plastic processing products. Products have a certain shape and size, and allow shaking within a certain range. The allowable range of the regular size of the product standard is called tolerance. Products within tolerance range are qualified products, and those beyond tolerance are unqualified products, foreign products or waste products. 标准上规则的公差是消费单位和运用单位都能接受的尺度，是产品交货的依据。 The shape size includes section size and length size. Section size refers to the diameter of round steel, the edge length and diagonal length of square steel, the thickness and width of flat steel, the thickness and width of steel plate, the difference between the same plate, the shape and edge thinning (see flatness defects), the outer diameter and wall thickness of steel pipe. Over-tolerance of various shapes and sizes includes roundness, deflection, bending, modification, ladle bending, waviness, sickle bending, tower shape of plate coil, axis perpendicularity of profiled material, angular defect of products with edges and corners, convexity of plate, same plate difference, three-point difference, same strip difference (see plate shape defect), uneven wall thickness, bamboo joint, etc.
The size is beyond the scope of the rules. It is usually used in mechanical processing.
On the request for higher dimensional accuracy, the general stop marking such as 10 +0.025, the request for form and position tolerance such as coaxiality tolerance 0.01, etc.
When the tolerance is not marked, it is free tolerance. Guaranteed by the processing equipment, GB/T 1804 regulates the tolerance range of linear dimension, that is, free tolerance.
Dimensional overshoot is usually caused by improper operation or improper process.