Drag or Roller Cone Underreamers: Clean and lubricate your underreamer after each use and store in a dry area. Periodically disassemble the underreamer and lubricate the piston and check on the condition of the cup seal and compression spring. Insure that there is no dirt in the system that hinders flow of air or fluid. Check the replaceable carbide jet plug (if you have one installed) for abrasive wear. Note you can adjust the fluid flow by changing the jet plug diameter and for your convenience we use a standard tricone rock bit jet. Check the rubber cup seal for edge wear and the actuator spring for strength.

Replacement of the underreamer arm is a simple operation. First remove the pin retaining bolt, and then remove the pin using a punch or round bar. The blade or roller cone arm is then easily removed. To check the piston assembly, remove the top sub and pull the piston assembly out of the body to check the jet plug, cup seal and actuator spring.

Drag Underreamers need the blades replaced, when the Tungsten Carbide coating becomes worn. Roller Cone Underreamers, need the roller cone assembly replaced when the teeth, buttons or bearings become worn. If the underreamer is a custom size we may require the complete assembly to be returned for reworking the roller arms. If you have any technical questions please contact us.