Nano Ic Engine

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  • Topic: Gear, Gears, Pinion
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Unit-4: Screw thread and Gear measurement: 
Unit-4: Screw thread and Gear measurement Hareesha N Gowda Dept of Aeronautical Engineering DSCE, Bangalore-78

Terminology of screw threads: 
Terminology of screw threads

Screw thread- definition: 
Screw thread- definition 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 threads.

Types of thread: 
Types of thread External thread : a thread formed on outside of a work piece is known as external thread. Example: on bolts or studs etc. Internal thread : a thread formed on inside of a work piece is known as internal thread. Example: on a nut or female screw gauge.

Screw thread - use: 
Screw thread - use Screw threads are used: To hold parts together-act as fastners (ex: V-threads) To transmit motion & power ( Square, Acme threads)

Screw Thread terminology: 
Screw Thread terminology

Screw Thread terminology: 
Screw Thread terminology Pitch : The distance from a point on a screw thread to a corresponding point on the next thread measured parallel to the axis. Lead The distance a screw thread advances in one turn. For a single start threads, lead=pitch, For double start, lead=2xpitch, & so on. Thread Form : The cross section of thread cut by a plane containing the axis. 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’

Screw Thread terminology: 
Screw Thread terminology 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’. 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. Flank: It is the Thread surface that connects crest with root. Depth of thread : It is the distance between crest and root measured perpendicular to axis of screw.

Screw Thread terminology: 
Screw Thread terminology Angle of thread : Included angle between sides of thread measured in axial plane. Helix angle : Angle that the thread makes with plane perpendicular to thread axis. Flank angle : It is half the included angle of the thread. Addendum : It is the distance between the crest and the pitch line measured perpendicular to axis of the screw. Dedendum: It is the distance between the pitch line & the root measured perpendicular to axis of the screw.

MEASUREMENT OF VARIOUS ELEMENTS OF THREAD: 
MEASUREMENT OF VARIOUS ELEMENTS OF THREAD To find out the accuracy of a screw thread it will be necessary to measure the following: 1) Major diameter. 2) Minor diameter. 3) Effective or Pitch diameter. 4) Pitch 5) Thread angle and form

Measurement of major diameter: 
Measurement of major diameter The instruments which are used to find the major diameter are by Bench micrometer Bench micrometer

Ordinary micrometer:: 
Ordinary micrometer: The ordinary micrometer is quite suitable for measuring the external major diameter. It is first adjusted for appropriate cylindrical size (S) having the same diameter (approximately).This process is known as ‘ gauge setting’ . After taking this reading ‘ R the micrometer is set on the major diameter of the thread, and the new reading is ‘R2

Measurement by Bench micrometer:: 
Measurement by Bench micrometer:

Measurement by Bench micrometer:: 
Measurement by Bench micrometer: For getting the greater accuracy the bench micrometer is used for measuring the major diameter. In this process...
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