Apparatus for measuring circularity of central hole of camshaft

The utility model discloses an apparatus for measuring the circularity of a central hole of a camshaft. The apparatus comprises a measuring rod and a ball body, wherein the measuring rod and the ball body are molded as a whole. The measuring rod includes a handle, a transition segment and a measuring head. The transition segment is positioned between the handle and the measuring head. The transition segment has a cross section shaped like an isosceles trapezoid. The top end of the measuring head is equipped with an arc groove, and the ball body is fixed in the arc groove. The axes of the handle, the transition segment and the measuring head and the central point of the ball body are on the same line. When the apparatus is in use, a user selects two apparatuses having two ball bodies different in dimension on the basis of the dimension of a central hole of a to-be-measured camshaft, coats inkpad on the two ball bodies, slowly puts the two ball bodies, having two dimensions and coated with the inkpad, into the central of the camshaft twice to make marks, then directly observes the mark of each ball contacting the central hole, and finally obtains a determination result visually. The apparatus is simple and convenient to operate, is low in workload and high in measuring efficiency, is convenient for people to check the circularity of a central hole of a camshaft, and helps to ensure the quality of products.