Usually, the inner circular arc surface is processed by a forming knife method on a lathe, and the disadvantage is that it is troublesome to manufacture the forming knife, and it is not easy to adjust the knife, especially in the mass production, which takes time and labor, and the inner arc is processed. The surface dimensional accuracy and surface profile are low, especially when the inner arc surface of the machined part is deep and small, and the machining requirements cannot be guaranteed. For this reason, we are in accordance with the existing equipment C512A and parts processing practice of the factory. Designed and manufactured a high-precision inner circular arc tool with simple structure and convenient operation. It is introduced as follows: