Screw Thread Terminology

A screw thread is the helical ridge produced by forming a continuous helical groove of uniform section on the external or internal surface of a cylinder or a cone. A screw thread formed on a cylinder is known as straight or parallel screw thread, while the one formed on a cone is known as tapered .

.

  1. Screw Thread terminology :-

  2.  Pitch: The distance from a point on a screw thread to a corresponding point on the next thread measured parallel to the axis.

  3.  Lead:- The distance a screw thread advances in one turn. For a single start threads, lead=pitch, For double start, lead=2xpitch, & so on. 

  4. Thread Form: The cross section of thread cut by a plane containing the axis. 

  5.  Major Diameter: This is the diameter of an imaginary cylinder, co- axial with the screw, which just touches the crests of an external thread or roots of an internal threads. It is also called as ‘Nominal diameter’

  6. Minor diameter: This is the diameter of an imaginary cylinder, co-axial with the screw which just touches the roots of an external thread or the crest of an internal thread. This is also referred to as ‘root’ or ‘core diameter’. 

  7.  Effective diameter or Pitch diameter: It is the diameter of an imaginary cylinder coaxial with the axis of the thread and intersects the flanks of the thread such that width of the threads & width of spaces between threads are equal. 

  8.  Flank: It is the Thread surface that connects crest with root.

  9. Depth of thread: It is the distance between crest and root measured perpendicular to axis of screw.

  10.  Angle of thread: Included angle between sides of thread measured in axial plane. 

  11.  Helix angle: Angle that the thread makes with plane perpendicular to thread axis. 
  12.  Flank angle: It is half the included angle of the thread. 

  13. Addendum: It is the distance between the crest and the pitch line measured perpendicular to axis of the screw. 

  14.  Dedendum: It is the distance between the pitch line & the root measured perpendicular to axis of the screw.

0 Comments
Tweets
Comments

Post a Comment

 
Support : Creating Website | Johny Template | Mas Template
Copyright © 2011. Mechanics Educational Materials - All Rights Reserved
Template Created by Creating Website Published by Mas Template
Proudly powered by Blogger