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FULL DIAMETER SHANK:
Equal to major diameter of thread. Produced by cut
thread or by roll thread on extruded blank.
Characteristic of machine bolts and cap screws.
|ROLLED THREAD: Threads are
cold formed by squeezing the blank between reciprocating
serrated dies. This acts to increase the major diameter
of the thread over and above the diameter of unthreaded
shank (if any), unless an extruded blank is used.Classes of thread are distinguished
from each other by the amounts of tolerance and allowance
specified. External threads or bolts are designated with
the suffix “A”; internal or nut threads with
Equal approximately to pitch diameter of thread.
Produced by roll threading a non-extruded blank.
Characteristic of machine screws.
The distance from a point on the screw thread to a
corresponding point on the next thread measured parallel
to the axis.
1A and 1B: For work of rough commercial quality
where loose fit for spin-on-assembly is desirable.
PITCH DIAMETER: The simple, effective diameter of
screw thread. Approximately half way between the major
and minor diameters.
2A and 2B: The recognized standard for normal
production of the great bulk of commercial bolts, nuts
MAJOR DIAMETER: The largest diameter of a screw
3A and 3B: Used where a closed fit between
mating parts for high quality work is required.
MINOR DIAMETER: The smallest diameter of a screw
4: A theoretical rather than practical class,
The distance a screw thread advances axially in one turn.
|CLASS 5: For a wrench fit.
Used principally for studs and their mating tapped holes.
A force fit requiring the application of high torque for
THREAD: Threads are cut or chased; the
unthreaded portion of shank will be equal to major
diameter of thread.