Abstract: Disclosed is a method and apparatus for machining a tubular workpiece to form an internally threaded coupling having a faced and chamfered end and a tapered counterbore. The method includes forming a tool support bar having a longitudinal axis and supporting on the tool support bar first and second tools having cutting edges and a thread cutting tool. The method further includes rotating the workpiece about its longitudinal axis and positioning the tool support bar relative to the workpiece such that the axis of the tool support bar and the workpiece lie in one plane and are substantially parallel to each other. The method further includes moving the support bar to chamfer and face the end of the workpiece with the first tool, moving the tool support bar to taper and counterbore the interior of the workpiece with the second tool, and moving the support bar to thread the tapered interior of the workpiece with the thread cutting tool.

Abstract: A method and apparatus for machining pipe collars having internally tapered coaxial threads is accomplished by providing a thread cutting tool having defined thereon a single thread groove forming tooth with first and second thread topping forming portions defined on opposite sides of the thread groove forming tooth. The first and second thread toppings are so designed and oriented with respect to the thread groove forming tooth that the first thread topping forms the top configuration of the first tapered threaded surface simultaneously with cutting the thread groove of the first tapered threaded surface. The second thread topping is so oriented with respect to the threaded groove cutting to that it remains clear of the first thread as the first threaded surface is being formed.

Abstract: A method and apparatus for machining pipe collars having internally tapered coaxial threads is accomplished by providing spaced sets of threading teeth on one side of a tool support bar of the numerically controlled machine with the spaced sets of threading teeth being oriented in generally parallel relation with the longitudinal axis of the tool support bar. The spaced sets of threaded teeth are then moved through the rotating collar by the tool support bar, following the desired internal taper with the orientation of the sets of thread forming teeth remaining substantially parallel with the axis of the tool support bar and the tool support bar being maintained in substantially parallel relation with the axis of the collar being formed. The sets of threading teeth form respective ones of the threaded tapers while the opposite set of thread forming teeth trace but remain clear of the thread being formed.