Outer arc diameter measuring tool

The utility model discloses an outer arc diameter measuring tool which comprises a main ruler extending along the left-right direction, scale marks are arranged on the main ruler, a vernier scale capable of sliding left and right is arranged at the top of the main ruler, the bottom surface of the main ruler is a horizontal plane, and an inclined first measuring clamping jaw is fixedly arranged at the position, close to the left end, of the bottom surface of the main ruler. The upper end of the first measuring clamping jaw is fixed to the main scale, the lower end of the first measuring clamping jaw extends leftwards in an inclined mode, an inclined second measuring clamping jaw is fixedly arranged at the bottom of the vernier scale, the upper end of the second measuring clamping jaw is fixed to the vernier scale, and the lower end of the second measuring clamping jaw extends rightwards in an inclined mode. And the working surface of the first measuring clamping jaw and the working surface of the second measur