Pipe Threading
The proper cutting of threads on pipe is overlooked by some mechanics. There are many different kinds of dies and different kinds of pipe to contend with. Steel pipe threads very hard and the adjustable dies should be used on it. These dies cut more easily and leave a cleaner thread than other dies when used on steel pipe. When threads are cut on wrought-iron pipe the adjustable dies should be used as they cut a better and cleaner thread than other dies. To preserve the life of the dies and the quality of the thread, oil is used freely while the dies are cutting.
Threads.—The standard thread on pipe and fittings is a right-handed thread. Left threads can be cut on the pipe and the fitting can be tapped with a left thread. When a fitting is tapped with a left thread it is marked so. The following table gives the standard number of threads that a die will or should be allowed to cut on the pipe:
| Size | Length, inches | Threads per inch | Threads per end |
|---|---|---|---|
| 3⁄8 | 9⁄16 | 18 | 10.825 |
| 1⁄2 | 3⁄4 | 14 | 10.500 |
| 3⁄4 | 3⁄4 | 14 | 10.500 |
| 1 | 15⁄16 | 111⁄2 | 10.800 |
| 11⁄4 | 1 | 111⁄2 | 11.500 |
| 11⁄2 | 1 | 111⁄2 | 11.500 |
| 2 | 11⁄8 | 111⁄2 | 12.930 |
To acquaint the beginner with iron pipe work, the following exercise is given. In it there are a great many of the actual problems that come up when the pipe is put in on a job. This is the last exercise that is required in this book. The sketch shows clearly just what the job is and below I have gone over each operation that is necessary to complete the job.
Materials Necessary.—Six feet of 1-inch black pipe; four 1-inch black ells; two 1-inch tee; one 1-inch right and left coupling; oil.
Tools Necessary.—Two 14-inch pipe wrenches, vise, pipe cutters, stock and 1-inch follower right and left die and reamer.
The vise is made secure on a bench or post, care being taken before it is put in place to provide room enough to swing the stocks. A length of 1-inch pipe is put into the vise and the vise clamped around it. The end of the pipe that is to be threaded should stick out through the vise about 9 inches. If there is a thread on this end, the dies should be run over it to make sure that it is a standard thread and to clean the threads. Before proceeding further with this exercise the dies and stocks will be described and their use shown.