Changeable combination tumbler wheel type key lock

A tumbler wheel type key lock operable by a key, comprising a lock case, a plurality of peripherally gated tumbler wheels supported for rotation about a common axis and each including center hub portions and rim portions encircling the hub portions, the key having an elongated shank and a plurality of wards projecting therefrom insertable into the center hub portions of the tumbler wheels, the center hub portions having shaped key apertures defining surfaces shaped to coact with the key wards to dispose the gates of said rim portions in alignment responsive to predetermined manipulation of the key and each center hub portion having a peripheral cylindrical bearing surface portion projecting beyond a side of its associated rim portion, supporting formations interposed between successive adjacent pairs of tumbler wheels defining spacers supported from the lock case outwardly of the tumbler wheel peripheries and having circular openings sized to receive the hub bearing surface portions journaled in nested relation therein to rotatably support the tumbler wheels about a common center axis, a control cam mechanism rotatable about said axis by the key inserted in the lock, a fence lever pivoted to a bolt having a depending nose adjacent the periphery of the control cam mechanism and a fence normally spaced above the tumbler wheel peripheries, and the control cam mechanism having means to link with said fence lever for retracting the bolt at a predetermined position when the tumbler wheel gates are positioned to receive the fence.