Page 49 - Microsoft Word - 4236

4.3.3 A PIPE CONICAL THREAD

A pipe conical thread is also a fastener and it is used for the higher requirements to sealing
joints.
Screw-thread sizes are determined by State Standard 6211-81. A thread taper is 1:16


( =1 47’24”). A thread profile is shown in fig.4.6. The size of a pipe conical thread and its
diameter is measured in the so-called basic plane which coincides with the bearing face of the
thread opening. They are fully identical with the analogical sizes of a cylinder pipe thread with the
same conventional size in this plane. Consequently, these parts with a pipe conical screw-thread can
be joined with the parts where the pipe cylinder thread of the same size is made.

Figure 4.6 - Pipe conical thread profile

Figure 4.7 - The conventional drawing of a pipe cylinder thread

The conventional denotation of this thread (fig. 4.7) consists of the Latin letter R (for external
thread) or R С (for internal thread), nominal size in inches and for the denotation of a left-hand
thread in case of need. An example of the conventional drawing of a pipe conical thread in an
opening with the size of 2 inches is R С2.

4.3.4 TRAPEZOIDAL SCREW-THREAD

A trapezoidal screw-thread is motion (translating). It is mainly used for transformation of
motion rotation on straight line motion. The sizes of a single trapezoidal screw-thread regulate State
Standard 9484-81, and a multiple-thread is State Standard 2439-81. The thread profile is shown in
fig. 4.8.

Figure 4.8 - A trapezoidal thread profile

49