EDM cutting machine for precision notching tubulars

A notch cutting machine for cutting an elongate linear notch using electrical discharge machining in an interior surface of an elongate metal oilfield tubular, such that the notch may be used to calibrate an oilfield tubular inspection machine, comprising:

• a machine base for engaging the interior surface of the tubular at a location adjacent where the notch will be cut;
• an electrically powered motor mounted on the machine base for rotating a motor shaft;
• an electrode support radially movable relative to the base;
• a linear translator including a cam mechanism rotated by the motor shaft for moving the electrode support a preselected linear distance in response to a preselected rotation of the motor shaft;
• an electrode having an electrode tip surface configured for cutting a preselected notch in the surface of the elongate metal tubular;
• an electrode head for supporting the electrode thereon;
• the electrode head being selectively positionable in a plurality of fixed orientation positions relative to the electrode support;
• a securing member for securing the electrode head in a desired fixed orientation position with respect to the electrode support;
• a fluid pressure responsive electrode holder for releasably supporting the electrode for movement with respect to the electrode head for mating engagement of the electrode tip surface with the interior surface of the elongate metal tubular and for thereafter selectively securing the electrode with respect to the electrode head;
• a power source exterior of the elongate metal tubular for supplying electrical power to the electrode;
• an electrical line for electrically connecting the power source and the electrode;
• and
• a liquid line for passing a coolant to an area adjacent the tip surface of the electrode for flushing the area where the notch is cut.

A method of cutting a notch in a surface of an elongate metal tubular, comprising:

• selectively positioning a machine base for planar engagement with the surface of the tubular at a location adjacent where the notch will be cut;
• mounting a motor on the base for rotating a motor shaft;
• movably mounting an electrode support relative to the base;
• moving the electrode support a preselected linear distance in response to a preselected rotation of the motor shaft;
• providing an electrode having an electrode tip surface configured for cutting a preselected notch in the surface of the elongate metal tubular;
• reducing fluid pressure to release the electrode for movement with respect to the electrode support for mating engagement of the electrode tip surface with the surface of the elongate metal tubular;
• thereafter applying fluid pressure to secure the electrode with respect to the electrode support;
• monitoring rotation of the motor shaft to determine the position of the electrode relative to the surface of the tubular;
• and
• supplying electrical power to the electrode to cut the notch.