The ring is set with a triangular-cut fancy vivid blue diamond, weighing 10.95 carats, and a triangular-cut diamond, weighing 9.87 carats, and dates from 1972.
The form of the tool used must exactly coincide with the profile of the thread to be cut, i. e. , triangular tools must be used for triangular threads, and so on.
使用的刀具外形必须正好与要切削螺纹的轮廓一致，即三角形刀具必须用于三角形螺纹等等。
3
Taking pivoting section cut a triangular graduation.