Apparatus for detecting flatness of large-dimension annular guide rail

The utility model discloses an apparatus for detecting flatness of a large-dimension annular guide rail, and belongs to the technical field of large-dimension measurements of machine tools. The apparatus includes a sector-shaped detection tool, handles, a radial level meter and a tangential level meter. The sector-shaped detection tool is a sector-shaped plate having a large arc upper end and a small arc lower end, the angle of the sector-shaped plate is [beta] degrees which is greater than 10 degrees and smaller than 30 degrees. The left side surface and the right side of the sector-shaped detecting tool are each provided with one pair of handles. The radial level meter is fixed close to the left side on the top surface of the sector-shaped detecting tool. The tangential level meter is fixed close to the bottom side in a direction perpendicular to that direction of the radial level meter. A large-dimension annular guide rail is divided, according to the [beta]-degree of the sector-shaped detecting tool, into n sector-shaped areas (n=360-degree/[beta]-degree). The level meters and the sector-shaped detecting tool are utilized and connected end to end, like measuring a linear guide rail, to measure in a movable manner along the circumference of the annular guide rail. A measured result is made into a curve which is an error of the flatness of the annular guide rail. The difficulty in detection of the flatness of the large-dimension annular guide rail is solved.