Take a piece of 1-inch pipe about 12 inches long and on one end cut a thread that is 2 inches long. Take a 1-inch coupling and screw it on this end until the end of the pipe is almost through the end of the coupling. At least four threads should be allowed at this end of the coupling. Now we have a piece of pipe 12 inches long having a thread 2 inches long on one end with a coupling on the thread. This is called a nipple holder. Now, to cut a nipple, cut a thread on a piece of pipe and cut the pipe off at any desired length, say 2 inches. Put the nipple holder in the vise with the coupling out from the vise about 8 inches. Take the 2-inch piece of pipe with a thread on one end, screw this thread into the coupling until it touches the pipe that has been screwed through from the other end. Now the stocks having the 1 dies and the follower in are put on the pipe. The follower will not go over the coupling, therefore take the follower out of the stock. Now the stock will slip over the coupling and the thread can be cut. With this procedure a nipple of any length can be cut. There are a number of patented nipple chucks on the market, but as they are not always at hand the above method is resorted to and serves every purpose.
To cut a long screw which comes in use frequently on vent pipe work, a piece of pipe 12 inches long is taken and a regular length thread is cut on one end, and a thread 4 inches long is cut on the other end. Then a coupling is cut while screwed on a pipe, so that a lock nut about 1⁄2 inch wide is made. The description and use of these long screws will come under screw pipe venting.
Now that the proper use of the tools has been explained, we will proceed with the exercise according to the sketch. With a length of pipe in the vise and the 1-inch dies in the stock, run over the thread on the pipe. Note that all the measurements are center to center. Screw an elbow on the pipe and measure off the first length, which we will take as 12 inches center to center. Place the rule on the pipe with one end of it at the center of the opening of the elbow just screwed on. Mark 12 inches off on the pipe. This mark represents the center of another ell. Now take another ell and hold the center of one outlet on this mark. It will readily be seen that to have the measurement come right, the pipe must be cut off at a point where it will make up tight when screwed into the ell. Therefore, about 1 inch will have to be cut off, making the pipe 1 inch shorter than where it was first marked. Cut the pipe, and before taking it out of the vise make a thread on the pipe still in the vise. After the thread is cut, take the reamer and ream out the burr that is on the inside of the pipe caused by the pipe cutter. An elbow can be screwed on this pipe. The next measurement is marked off as explained, the pipe cut, then the piece in the vise threaded and reamed. The measurements must be accurate and the dies should be adjusted to cut all threads the same depth. When the measurements are all out, there should be seven pieces of pipe, each piece having one thread. Now the threads on the other end can be cut except the 12 inch piece that screws into the right and left coupling. This thread is a left-handed thread and must be cut with the left dies. Change the dies now to the 1-inch left dies; turn the stock in the opposite direction of the right-hand thread, and the dies will cut the left thread. The pipe and the fittings can easily be put together as shown in the sketch by following the center to center measurements. The right and left coupling is the only fitting that will cause the beginner trouble. A right and left coupling can be used only when there is sufficient give to the pipe, that is, the two ends of the pipe to be coupled together are only 1⁄2 inch apart. To get the coupling in place to start the threads, the pipe must spread apart at least 2 inches. If the pipe cannot be spread that much, a right and left coupling cannot be used. The proper way to make up a right and left coupling is as follows:
Fig. 69. - F reads center of ell to end, C reads center of ell to center of valve, D reads center of valve to center of T, E reads center of T to center of ell.
Screw home the coupling on the right thread. Mark with a piece of chalk on the coupling and the pipe showing a point on each where the coupling makes tight. Take off the coupling and count the turns and make note of the number. Now do the same on the left thread and make a note of the number of threads. If the left thread has six turns and the right has four and one-half, then to insure that the left thread will be tight when the right thread is, the coupling must be put on the left thread one and one-half turns before it is started on the right thread. Now with four and one-half turns, the right and the left threads will both be tight. A little thought and practice will make this connection clear. If all the measurements in this exercise are not cut accurately, the right and left coupling will not go together.