A modular tool system is disclosed herein with a power unit, a battery, a controller, a sensor, and a plurality of tool modules. The hand-held sized power unit can include a motor housing and a motor with a shaft. The controller can variably control the shaft. Each tool module can include a housing, a work-engaging portion, a transmission linkage, and an identifier. The identifier is within a range of detection of the sensor when the housings are coupled. Each of the identifiers is distinguishable from other identifiers and the sensor transmits a different signal for each of the identifiers. The controller is configured to determine one of a plurality of different shaft speeds or one of a plurality of different torques to transmit through the shaft in response to the signal from the sensor indicating a particular identifier.
