形位公差 规格表
几何公差(GD&T)是以基准为参考精确规定零件形状、姿态、位置和跳动误差的设计方法。能控制尺寸公差无法表达的形状精度，对功能保证至关重要。
形状公差
Form Tolerance · 6个尺寸
方向公差
Orientation Tolerance · 3个尺寸
位置公差
Position Tolerance · 4个尺寸
跳动公差
Runout Tolerance · 2个尺寸
常见问题 (FAQ)
Why is GD&T (geometric dimensioning and tolerancing) necessary?
Dimensional tolerances alone cannot control form errors like straightness, circularity, and position. GD&T specifies the geometric accuracy required for function, improving quality and reducing defects.
What is a datum in GD&T?
A datum is a theoretically exact point, line, or plane used as a reference for geometric tolerances. Setting datum A as the reference plane lets you measure parallelism and perpendicularity from A. Datums are prioritized A, B, C.
What is the difference between position tolerance and concentricity?
Position tolerance controls deviation of a hole or pin center from its true position relative to a datum. Concentricity controls how closely two cylinder axes coincide. Position tolerance is more commonly used.