LATHE OPERATIONS - OD1645 - LESSON 1/TASK 3
a. General. A thread is a uniform helical groove cut on or in a cylinder
or cone.
Thread cutting on a lathe is one of the most exacting lathe
operations.
It requires a thorough knowledge of the principles and
procedures of thread cutting. It ties together a number of operations and
dimensions in such a way that accuracy must be maintained to achieve a
proper working thread.
Before attempting such operations, the operator
should have knowledge of the fundamental principles of threads and the types
in general use.
b. Screw Thread Terminology. The common terms (figure 38) and definitions
given below are used in screw thread work and will be used when discussing
threads and thread cutting.
FIGURE 38.
SCREW THREAD TERMINOLOGY.
(1) External or Male Thread.
A thread on the outside of a cylinder or
cone.
(2) Internal or
Female
Thread.
A
thread
on
the
inside
of
a
hollow
cylinder or bore.
(3) Pitch (P). The distance from a given point on one thread to a similar
point on a thread next to it, measured parallel to the axis of the cylinder.
The pitch in inches is equal to one divided by the number of threads per
inch.
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