Hydraulic stop

A hydraulic stop for use in drilling or countersinking operations comprising

• a rotatable body for rotating a tool about its axis;
• and
• a cage adapted to contact the surface of a workpiece when the tool has penetrated into the workpiece by a predetermined distance, and to actuate a trip mechanism comprising a plunger operated hydraulic valve as the tool penetrates the workpiece by more than the predetermined distance;
• wherein
• the trip mechanism is effective, when actuated, to allow the rotatable body to reduce in length parallel to the rotating axis of the tool;
• the plunger has an adjustable length;
• the cage is axially adjustable in relation to the body to set the predetermined distance at which the trip mechanism actuates;
• and
• a plurality of holes which are spaced around the circumference of the body allow drainage of coolant from the cage whatever its axial position.