A lock mechanism includes a cover plate positionable over a plurality of pin chambers in a cylinder housing wherein one or more of the pin chambers include an internal threaded portion. The lock mechanism includes one or more pin assembly caps that are operative to secure the cover plate to the cylinder housing of the lock by threadably engaging with threaded pin chambers. The pin assembly caps include an internal cavity sized to receive at least a portion of a pin assembly, such that threaded pin chambers and unthreaded pin chambers have substantially the same dimensions without substantially increasing the dimensions required for the lock mechanism. The pin assembly caps include a socket (e.g., a hex socket, a Phillips-type socket, or the like) that allow users to selectively remove and secure the cover plate to the cylinder housing common tools.