A power tool including an activation arm assembly having an actuator coupled to the activation arm assembly, the activation arm assembly being coupled to the structure and including a roller assembly having a roller, wherein actuation of the actuator causes the roller assembly to translate toward and engage the driver to initiate driving engagement between the driver and the flywheel; The activation arm assembly further includes a follower arm that engages the roller, the follower arm including a first mounting portion and a second mounting portion, the second mounting portion being pivotally coupled to the actuator and slidingly engaged with the carriage, the first mounting portion being biased in a direction toward the driver. The follower arm has a non-linear profile.