真位置

定義

基準に対する位置ずれを管理する幾何公差。

フロントマターの定義を基準にし、段取り・加工・検査で同じ意味として扱います。

公式/ルール

• For a 2D hole-center check, a common calculation is TP = 2 × sqrt((ΔX)^2 + (ΔY)^2) in the drawing unit.
• Evaluate true position against the active datum structure, not against free-state coordinates.

代表的な範囲

• Review the tolerance as a diametrical zone and confirm whether MMC/LMC modifiers change the effective limit.
• Check X/Y drift together; a single-axis result can look acceptable while combined position does not.

現場シナリオ

• Use true position to review hole patterns before committing rework on a precision plate.
• Compare measured center drift with the active datum before moving offsets on a multi-feature part.

よくある問題/トラブルシュート

• If holes fail true position unexpectedly, verify both datum lock and hole-center measurement method before reworking parts.
• If correction makes one feature better but another worse, check whether the active datum or pattern origin is wrong.

関連ツール

• True Position Calculator
• Gdt Reference