形位公差 規格表
幾何公差(GD&T)是以基準為參考精確規定零件形狀、姿態、位置和跳動誤差的設計方法。能控制尺寸公差無法表達的形狀精度，對功能保證至關重要。
形狀公差
Form Tolerance · 6個尺寸
方向公差
Orientation Tolerance · 3個尺寸
位置公差
Position Tolerance · 4個尺寸
跳動公差
Runout Tolerance · 2個尺寸
常見問題 (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.