Arc radius measuring tool

The utility model relates to an arc radius measuring tool which is used for measuring the radius of an elbow pipe after metal pipeline elbow pipe processing in the industries of chemical engineering,boilers and the like, and comprises a measuring tool body, fixed measuring jaws which are tightly attached to the arc surface of the inner arc of the elbow pipe of a workpiece during working are arranged on two sides of the upper part of the measuring tool body, and the distance between the two fixed measuring jaws is the chord length of a measured arc; a slide way is arranged in the middle of themeasuring tool body, a measuring rod which can freely slide and stretch along the slide way is arranged in the slide way, the measuring head at the upper end of the slide way abuts against the middlepoint of an arc to be measured after the slide way stretches out, and the chord height of the arc to be measured is measured through the measuring rod. The contour line of the measuring cam is contacted with the lower end of t