The invention provides a method and a device for detecting radial runout of a lathe spindle in a
machining state. The device comprises a host computer, a core rod absorbing and holding
assembly and a dynamic adjusting and testing
assembly, wherein the core rod absorbing and holding
assembly is fixed on a to-be-machined
round bar, and the core rod is absorbed on smooth tempered glass by a strong
magnet; the dynamic adjusting and testing assembly is mounted on a bracket with a
laser displacement sensor and a nylon push block as cores; the bracket can be arranged at any static part of a lathe body by a
magnet base. When the radial runout of the lathe spindle is measured in the
machining state, the nylon push block is driven by a
differential screw mechanism to push the core rod on the tempered glass, meanwhile, displacement signals of the core rod during rotation are picked by the high-precision
laser displacement sensor and transmitted to the computer for
processing and displaying, fine adjustment is performed until a peak-to-
peak value of a measured value is the minimum, and eccentricity is eliminated once; the measured value is filtered by the host computer, measurement signals with the same frequency as rotating speed are eliminated, and a finally obtained variable range of the measured value is the radial runout affecting
machining quality.