Elements of plumbing . pipecut, then the piece in the vise threaded and reamed. The 116 ELEMENTS OF PLUMBING measurements must .be accurate and the dies should beadjusted to cut all threads the same depth. When themeasurements are all out, there should be seven pieces ofpipe, each piece having one thread. Now the threads onthe other end can be cut except the 12 inch piece that screwsinto the right and left coupling. This thread is a left-handed thread and must be cut with the left dies. Changethe dies now to the 1-inch left dies; turn the stock in theopposite direction of the right-hand thread
Elements of plumbing . pipecut, then the piece in the vise threaded and reamed. The 116 ELEMENTS OF PLUMBING measurements must .be accurate and the dies should beadjusted to cut all threads the same depth. When themeasurements are all out, there should be seven pieces ofpipe, each piece having one thread. Now the threads onthe other end can be cut except the 12 inch piece that screwsinto the right and left coupling. This thread is a left-handed thread and must be cut with the left dies. Changethe dies now to the 1-inch left dies; turn the stock in theopposite direction of the right-hand thread, and the dieswill cut the left thread. The pipe and the fittings can easilybe put together as shown in the sketch by following thecenter to center measurements. The right and left couplingis the only fitting that will cause the beginner trouble. Aright and left coupling can be used only when there issufficient give to the pipe, that is, the two ends of the pipeto be coupled together are only J^ inch apart. To get the. Fig. 69.—F reads center of ell to end, C reads center of ell to centerof valve, D reads center of valve to center of T, E reads center of T tocenter of ell. coupling in place to start the threads, the pipe must spreadapart at least 2 inches. If the pipe cannot be spread thatmuch, a right and left coupling cannot be used. The properway to make up a right and left coupling is as follows: Screw home the coupling on the right thread. Mark witha piece of chalk on the coupling and the pipe showing a pointon each where the coupling makes tight. Take off thecoupling and count the turns and make note of the number. PIPE THREADING 117 Now do the same on the left thread and make a note of thenumber of threads. If the left thread has six turns and theright has four and one-half, then to insure that the leftthread will be tight when the right thread is, the couplingmust be put on the left thread one and one-half turns beforeit is started on the right thread. Now with four a
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