中径是通过螺纹轴向截面内牙型上的沟槽和凸起宽度相等处的假象圆柱的直径（如图中d2）。中径是确定螺纹几何参数和配合性质的直径。
检测圆锥管螺纹基面中径的方法有很多，但测量过程复杂。
There are many ways to measure base-level pitch diameter of cone-shaped thread.
提供了一种简便易行、准确可靠的测量内螺纹单一中径的手段。
A simple, easy to use, correct and reliable for measurement of single pitch diameter of inner thread is provided.
介绍自行开发的内螺纹中径测量装置的构成、原理和使用方法。
This paper introduces the structure, the principle and the operation of a device measuring inside screw developed by the authors.
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