An adjustment assembly for raising and lowering a rotary cutter includes a table plate, a carriage assembly there below for supporting the rotary cutter and a lift handle which mounts on the carriage assembly and extends above the table plate to provide rapid manual raising and lowering of the carriage assembly. The carriage assembly is mounted on a support assembly and is disengageable therefrom to allow the rapid raising and lowering. Preferably, the lift handle is insertable through an opening in the table plate and into an opening in the carriage assembly and rotatable to disengage an engaging member of the carriage assembly from the support assembly via a camming engagement. A vertical adjustment mechanism for finely adjusting the carriage assembly height may include an adjusting screw which the engaging member engages for fine vertical adjustment and disengages for rapid vertical adjustment.