Fig. 617.
The pipe vise is especially a bench tool; it is designed to “grip” pipes of various sizes while they are being threaded, cut off or otherwise operated upon.
A parallel or ordinary bench vise will only grip a pipe on two opposite sides, and, if tightened, the strain will easily collapse it, owing to its hollow form; but a pipe vise is so made that it presses upon four points, as the jaws or holding portions are formed V shaped, instead of parallel.
Some pipe vises are formed of two pivoted discs instead of jaws, having semicircles or recesses, which fit all diameters of pipes up to two inches, and bear on the outside of the pipe all around.
It is an improvement to have the upper portion of the vise hinged at one side, and fixed with a pin or collar at the other, as by opening the jaws it renders more convenient the removal or insertion of the pipe to be operated upon.
The upper Fig. [618] on page 342 represents an indispensable tool for cutting pipe threads by hand; one handle—of which there are two—is shown in the figure immediately beneath the pipe stock and die, which is the familiar name of the combination. The guard in the illustration is thrown open to allow the die to be removed or exchanged. Fig. [620] represents the latter; solid steel dies are commonly used, but adjustable dies are made. Figs. [621] and [622] are bushings to fit in the end of the stock to guide the pipe; there is one bushing for each size of pipe.
Fig. [623] shows a nipple-holder which is used to hold short pieces of pipe by the thread upon one end, while the die is applied to cut a thread upon the other end. This tool is generally used in a pipe cutting machine, which is operated by power, but it can also be held in a common vise.
Note.—The die may be centered on the nipple described above by placing in the die stock a guide bushing that will easily ride over the nipple holder. The thread can now be cut until the die just touches the nipple holder, and there will be practically no blank space between the threads on the ends. After the die has been backed off the nipple can be removed from the holder by unscrewing the center with a monkey wrench. A nipple holder should be made for each size of pipe that is cut and threaded by hand. A piece of pipe with a coupling on its end may be used as an improvised nipple holder.