Bolt Thread

Topics: Unified Thread Standard, Screw thread, British Standard Whitworth Pages: 7 (1759 words) Published: May 11, 2013
Bolt thread experiment was conducted to examine the major diameter, minor diameter, angle and the pitch of the bolt thread. Other than that, the purpose of this experiment is to compare the measured data with the standard thread from literature. The experiment was carried out by taking the measurement using optical projector. The shadow or the image of the bolt is traced and magnified on the broad of the optical profile projector. The crest and the toot of the bolt thread were picked to lie on the horizontal line on the broad of the optical comparator. The measurements were repeated to improve the accuracy of measurements. Introduction/Theoretical background

Bolt is a metal pin with a head at one end and a thread at the other end. A bolt is an externally threaded fastener that is inserted through holes on the parts that are screwed into a nut on the opposite site. Screw thread

There is no other device in the entire field of mechanic that can compare with the screw thread. Highly adapted and extremely versatile, therefore it has become an indispensable unit in our daily life. It takes a moment’s reflection to appreciate the utter dependence of our society upon this simple item. Our wonderfully industrialized civilization is built upon the machine. And the generic term machine encompasses all manner of invention and mechanisms which are in turn, based upon the six fundamental “machines”, they are; the inclined plane, the wedge, the screw, the lever, the wheel and the pulley. Thread has been utilized for holding parts together, making adjustment to tools and instruments. The thread also is used to transmitting power and motions for hundreds of years. Screw, inclined plane and the wedge are fundamentally related. A thread is the wrapping for the wedge around a cylinder in a spiral, thereby creating a helix or rudimentary screw. Today, threads are mass-produced by tops, dies, thread rolling, thread milling and grinding to exacting standards of an accuracy and quantity control. Some of the thread terminologies for thread part measured in this experiment are given below; Screw thread: A ridge of uniform section in the form of a helix on the external or internal surface of a cylinder, or in the form of a conical spiral on the external or internal surface of a cone or frustum of a cone. Major diameter: On a straight thread, the major diameter is the diameter of the coaxial cylinder that would bind the crest of an external thread or the root of an internal thread. On a taper thread, the major diameter at a given position on the thread axis is the diameter of the minor cone at that position. Pitch: That distance from a point on a screw thread to a corresponding point on the next thread, measured parallel to the axis. Angle (included angle): The angle between flanks, measured in an axial plane. Optical comparators

Optical compares is a projector device used to measure a sample of material which its length cannot be measured by the other devices. Optical comparator projects an enlarged shadow onto a screen where it may be measured by some apparatus. It is often used when the work piece is difficult to check by other methods. Optical comparators are particularly suited to check on extremely small or odd – shaped parts, which would be difficult to inspect without the use of expensive gages. Example of sample like as thick of thin metal plate, fine wire diameter and pitch of bolt. This device is operated based on the principle of image enlargement, and measure with the fixed enlargement factor. In the experiment, sample of material is a bolt 0.5 inch B.S.W image in the screen as shown below;

British Standard Whitworth (BSW)
British Standard Whitworth (BSW) is one of a number of imperial unit based screw thread standards which use the same bolt heads and nut hexagonal sizes. The original Whitworth thread form was proposed by Joseph Whitworth in 1841 to replace various proprietary fasteners. This standard specifies a 55°...
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