A device for correcting tool lengths and tool radii, of a machine having a machine housing with a spindle for mounting the tool, and which is equipped with position or path measuring systems, comprising, a feeler housing, mounting means for mounting said feeler housing on said machine adjacent the tool holder spindle, a first feeler pin mounted in said feeler housing extending along the Z-axis and having a first switching portion, a second feeler pin mounted on said feeler housing and extending along the X-axis perpendicular to the first feeler pin and spaced in height from said first feeler pin, gear means connecting said first and second pins together for movement of the respective pins along their respective axis in response to the movement of the other, at least one limit tracer disposed in the Z-axis in said housing, at least one inductive transmitter disposed along the X-axis of said housing, stop means in said housing, spring means urging said first and second feeler pins outwardly to apply against said stop means, each limit tracer in the Z-axis being switchable by the associated switching portion of said first and second feeler pins, an inductive transmitter extending parallel to the axis of said second feeler pin and being movable in the X-axis and disposed relative to said second feeler pin so that it will be switched by said switching portion thereof.