What is GPS in dimensional metrology?

GPS (Geometrical Product Specifications) is a framework of ISO standards for specifying and verifying geometry of workpieces. ISO 14405-1 specifically covers linear size tolerances and defines how size is specified and interpreted.

What is the default size specification in ISO 14405-1?

The default specification operator is the two-point size (LP — local size measured between two opposing points). If no modifier is indicated on the drawing, two-point size applies. This is the traditional caliper/micrometer measurement.

What are the special specification operators?

ISO 14405-1 defines several special operators: GG (least-squares/Gaussian size), GX (maximum inscribed size for holes), GN (minimum circumscribed size for shafts), CC (circumference diameter), and others for specific measurement needs.

How does ISO 14405-1 relate to ISO 286?

ISO 286 defines the ISO system of limits and fits (IT grades, fundamental deviations). ISO 14405-1 defines HOW the size is measured/interpreted. Together they fully specify size: ISO 286 gives the limits, ISO 14405-1 gives the measurement method.

What is the envelope requirement (Ⓔ)?

The envelope requirement (Ⓔ modifier per ISO 14405-1) requires that the feature does not violate a perfect-form boundary at MMC. This links size and form, effectively requiring the feature to fit inside a perfect gauge at maximum material size.

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GPS 公差計算器 — ISO 14405-1

ISO 14405-1 GPS 尺寸公差參考。輸入公稱尺寸與配合，即可查看符合 GPS 框架的規格運算子、極限與解釋。

ISO 14405-1ISO 286GPS 框架

公稱尺寸 (mm)

配合 / 公差

尺寸規格運算子

包容要求

快速預設

結果

圖面規格

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上限

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下限

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公差帶

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運算子說明

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ISO 14405-1 規格運算子

符號	名稱	說明	典型用途
LP	兩點尺寸	兩相對點之間的距離（預設）	卡尺/千分尺測量
GG	最小二乘法尺寸	高斯（最佳擬合）直徑	三座標測量機、圓度測量儀
GX	最大內接尺寸	可容納於內部之最大完美圓柱體	孔（功能量規）
GN	最小外接尺寸	能包覆該特徵的最小理想圓柱體	軸（功能量規）
CC	周長直徑	由周長測量得出的直徑	捲尺
CA	面積直徑	由截面積得出的直徑	光學測量

預設規則： 若未指定規格運算子，則依 ISO 14405-1 適用 LP（兩點尺寸）。此為傳統的卡尺/千分尺測量方式。

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結果

ISO 14405-1 規格運算子

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