Abstract: The apparatus includes a drill motor and a cutter drive mechanism coupled with the drill motor for rotating and advancing a rotary cutter along an axial direction, and a clamping mechanism having a pair of opposed clamping members and an actuator that moves the clamping members relatively toward and away from each other for clamping and releasing a workpicce. The actuator is a fluid-operated cylinder such as an air cylinder, and a fluid circuit associated with the cylinder is arranged such that in a normal state of the fluid circuit the cylinder urges the clamping members together to clamp the workpiece. The apparatus includes a control valve that can be operated to cause the fluid circuit to control the cylinder to move the clamping members apart.

Abstract: An adjustable portable irrigation dam for use in an irrigation ditch is operative to selectively raise the water level upstream of the dam thereby permitting removal of water for irrigation of crops. The dam includes an elongated sheet support member extending transversely across the irrigation ditch and being rotatably supported in members selectively positioned on opposite sides of said ditch to resist forces thereon so that rotation of said support member will selectively raise and lower one end portion of a sheet of a flexible material into and out of blocking relation to the irrigation ditch. Retaining mechanism is connected to the sheet support member for selectively retaining the support member and the flexible sheet in a selected position.