Fastener driving tool

A fastener driving tool includes a housing defining a handle portion and a head portion with a nose portion extending therebelow. Mounted within the head portion is a cylindrical sleeve within which is reciprocally mounted a drive piston. A driver for driving fasteners is secured to the drive piston and reciprocates therewith. The tool includes a drive power control for controlling the penetration of the fasteners into a workpiece. The drive power control includes a choke encircling the sleeve to impede the flow of exhaust air from beneath the piston and under the sleeve during a driving stroke. The choke may be moved to a position spaced from the cylindrical sleeve wherein the flow of fluid below the piston is not inhibited. In addition, the tool includes a safety member with a workpiece engaging portion of at least one wear block secured thereto to engage the workpiece and protect the safety member from undue wear.