In an embodiment, a lock mechanism has a lock shaft, a motor, and a lock cylinder, wherein the motor rotates a cog that moves the lock cylinder into and out of the lock shaft. The lock cylinder is oriented concentric to an axis about which the lock cylinder rotates. Rotating the cog causes the lock cylinder to rotate about the axis, which in turn causes the lock cylinder to more into and out of the lock shaft in a direction along the axis. In an embodiment, the cog has no translational motion in a direction parallel to the axis. The lock cylinder may have grooves, and the cog may engage the grooves. Rotating the cog may causes the lock cylinder to rotate with the cog, and the cog to slide within the grooves as the lock cylinder moves along the axis.