A combinating tumbler lock featuring zero clearance between the lock plug and mounting shell including: a mounting shell having a central throughbore with a front section having a first, greater diameter and including longitudinal locking grooves, a rear section having a second smaller diameter and including longitudinal stopping grooves, and a tapered transition section between the front and rear sections; a lock plug for selective rotation within the mounting shell and having three sections corresponding in diameter to the sections in the mounting shell, the lock plug front section including a tumbler receiving opening, the lock plug rear section including a cam-receiving structure and a first radial throughbore, the lock plug also including a second radial throughbore between the front section and the tapered section; a tumbler disposed in the lock plug for selective engagement with the longitudinal locking grooves of the shell; a spring loaded stop comprising two spherical balls actuated by a compression spring disposed within the first radial throughbore to provide positive stop positioning and feel by selective engagement with the stopping grooves; and a spring loaded bearing in the form of two spherical balls actuated by a compression spring and disposed within the second radial throughbore.