Decoupling mechanism for power tools

A decoupling mechanism for a tool having a motor operatively connected to a drive shaft that drives a rotatable tool member, comprising:

• a shaft gear disposed around and displaceable along the drive shaft, said shaft gear being driven by the motor;
• at least one pressure plate disposed on the drive shaft on a first side of said shaft gear and configured for rotation with the drive shaft;
• a spring assembly disposed on the drive shaft on a second side of said shaft gear configured to apply a normal force on said shaft gear to frictionally transfer motor torque from said shaft gear to the pressure plate;
• at least one cam disposed longitudinally with respect to the drive shaft between said spring assembly and said shaft gear, wherein all of said at least one cam are disposed on one side of said shaft gear;
• at least one shallow receiving structure and at least one deep receiving structure opposing said spring assembly;
• wherein when said at least one cam is engaged in said at least one shallow receiving structure, said spring assembly transfers a normal force on said shaft gear which applies said normal force on said at least one pressure plate to couple the motor to the drive shaft, and when said at least one cam is engaged in said deep receiving structure, there is substantially no spring force in said spring assembly, and substantially no normal force is applied to said at least one pressure plate from said spring assembly so that said shaft gear is uncoupled from the drive shaft.