Stapler and method for the attachment of steel framing

A staple driving tool and a method for clamping and stapling together two or more steel workpiece layers as in light gauge steel framing for residential and commercial buildings, truss assembly, and the like. The stapling tool has a guide body and a jaw assembly supporting an anvil. The jaw assembly is pivoted to a mounting bar extending along and beneath the tool magazine. The jaw is pivotable between a normal open position and a closed position wherein it clamps the steel workpiece layers to be joined between the anvil and the guide body prior to stapling. The jaw is pivotable by an air cylinder actuated toggle mechanism. An air valve normally connects the air cylinder to atmosphere. When actuated, the air valve connects the air cylinder to a source of pressurized air, shifting the jaw to clamping position. The air valve may be actuated by one of the tool safety and the tool trigger. Thereafter, the tool operator may release the trigger or safety to reposition the tool, or the operator may complete actuation of the trigger to drive a staple through the clamped steel layers, causing the anvil the clinch the staple against the steel layers. As the staple approaches the steel layers to be joined, a member enters between the staple legs to prevent buckling thereof until the staple penetrates the steel layers, whereafter the member is shifted by the staple crown and driver from between the legs to accommodate the staple crown and driver.