5-37) will cut American Pipe Thread only. It comes in
The tap diameter, from end to end of threaded
a variety of sizes for cutting threads on pipe with
portion, increases at the rate of 3/4 inch per foot. All
the threads on this tap do the cutting, as compared to
the straight taps where only the nonchamfered portion
A rethreading die as shown (fig. 5-37) is used
does the cutting.
principally for dressing over bruised or rusty threads
on screws or bolts. It is available in a variety of sizes
Dies are made in several different shapes and are
for rethreading American Standard Coarse and Fine
of the solid or adjustable type. The square pipe die (fig.
threads. These dies are usually hexagon in shape and
can be turned with a socket, box, open-end, or any
wrench that will fit. Rethreading dies are available in
sets of 6, 10, 14, and 28 assorted sizes in a case.
Round split adjustable dies (fig. 5-38) are called
"button" dies and can be used in either hand diestocks
or machine holders. The adjustment in the screw-adjust-
ing type is made by a fine-pitch screw that forces the
sides of the die apart or allows them to spring together.
The adjustment in the open adjusting types is made by
three screws in the holder, one for expanding and two
for compressing the dies. Round split adjustable dies are
available in a variety of sizes to cut American Standard
Coarse and Fine threads, special form threads, and the
standard sizes of threads that are used in Britain and
Figure 5-37.--Types of solid dies.
other European countries. For hand threading, these
Figure 5-38.--Types of adjustable dies.