Abstract: A D.C. tool switch assembly is provided with a pair of field effect transistors (FETs) maintained internally of the housing. The switch assembly is configured of a number of subassemblies maintained within the housing, including a contact subassembly having the motor and battery contacts and a pair of pivoting contacts. The field effect transistors are maintained on a second subassembly which nests within the housing and is substantially orthogonal to the contact subassembly. A post passes through the pair of FETs and is formed to engage a heat sink on each of opposite sides of the switch housing. The heat sinks are separate and distinct from each other and individually formed. Each of the heat sinks makes close contacting engagement with an associated one of the FETs. The post provides for interconnection between the FETs and the pair of heat sinks.