Method and contrivance of machining pipe joints

Claim 1

METHOD OF MACHINING A READ ON A TUBULAR WORKPIECE, SUCH AS A PIPE COUPLING, HAVING TAPERED COAXIAL THREADS INCREASING IN DIAMETER OUTWARDLY FROM THEIR JUNCTION INTERMEDIATE THE ENDS OF THE WORKPIECE, SAID METHOD COMPRISING: ROTATING THE WORKPIECE ABOUT ITS AXIS AT A HIGH ANGULAR VELOCITY; ARRANGING A RELATIVELY ELONGATED TOOL SUPPORT FOR LONGITUDINAL RECIPROCATION THROUGH THE WORKPIECE IN A FEEDING DIRECTION INTERSECTING THE AXIS OF THE WORKPIECE AT AN ANGLE EQUAL TO THE ANGLE OF TAPER OF THE THREAD: FIXEDLY POSITIONING A PAIR OF CUTTING TOOLS ON THE SUPPORT IN FIXED LONGITUDINALLY SPACED RELATION THEREALONG AND PROJECTING LATERALLY IN OPPOSED FIRST AND SECOND DIRECTIONS THEREFROM; SHIFTING THE SUPPORT LATERALLY IN SUCH FIRST DIRECTION TO ENGAGE ONE CUTTING TOOL WITH THE WORK AT THE ENTRANCE AND OF THE WORK; ADVANCING THE SUPPORT IN THE FEEDING DIRECTION THROUGH THE WORK AT A RATE COORDINATED WITH THE ANGULAR VELOCITY OF THE WORK AT A CUT A THREAD EXTENDING FROM SAID ENTRANCE END TO SAID JUNCTION; SHIFTING THE SUPPORT IN SUCH SECOND LATTERAL DIRECTION TO ENGAGE THE OTHER CUTTING TOOL WITH THE WORK WHILE CONTINUING THE ADVANCE OF THE SUPPORT IN THE FEEDING DIRECTION TO CONTINUE THE CUTTING OF THE THREAD FROM THE JUNCTION TO THE EXIT END OF THE WORKPIECE; SHIFTING THE SUPPORT IN SUCH FIRST DIRECTION AN AMOUNT SUFFICIENT TO DISENGAGE BOTH CUTTING TOOLS FROM THE WORK; AND RETRACTING THE SUPPORT THROUGH THE WORKPIECE IN THE DIRECTION OPPOSITE TO THE FEEDING DIRECTION.