A lock pin assembly used for clamping two plates together, that have aligning bores for receiving the lock pin assembly. The lock pin assembly includes radially extending pins that can be forced outwardly from the center of a lock pin housing forming a part of the lock pin assembly. The actuator pins are forced outwardly and cooperate with a tapered surface on a bottom plate to create a clamping force relative to an end of the lock pin housing supportable on a top plate. The lock pin housing has cam tracks on an outer side thereof, and an actuator ring surrounds and supports the pin and carries cam followers sliding in the cam tracks. The cam tracks are made such that relative rotation of the lock pin housing and the actuator ring changes the axial location of the actuator ring along the housing. The actuator ring rests on the top plate and when the actuator pins are released so they can retract and the lock pin housing and the actuator ring are relatively rotated, the lock pin housing is raised relative to the two plates to aid in removing the lock pin assembly.