1. Screw Thread Measurement
Prof. M. M. Joke
Chapter 5
Screw Thread Measurement

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Errors in Threads
Major diameter error – Cause interference with the mating threads or reduction in the flank contact or weakness by reduction of the wall thickness.
Minor diameter error - Cause interference with the mating threads or reduction in the flank contact or weakness by reduction of the cross section of the root.

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Errors in Threads
3.Effective diameter error – Determine the amount of slackness or interference between the flanks of mating threads.
4.Errors or Pitch and Thread angle – Result in progressive tightening and interference on assembly.

6. Pitch Errors Progressive Error Periodic Error Drunken Error
Prof. M. M. Joke
Pitch Errors
Progressive Error
Periodic Error
Drunken Error
Erratic or Irregular Error

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10. Disturbances in the machining setup.
Prof. M. M. Joke
Erratic Errors – Vary in an irregular manner along the length of the thread. Their causes are difficult to identify. Possible causes are:
Fault in the machine.
Irregular cutting action resulting from non-uniformity in the material of the screw.
Disturbances in the machining setup.

11. Measurement of different elements of Thread
Prof. M. M. Joke
Measurement of different elements of Thread
Major diameter
Minor diameter
Effective diameter
Pitch

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Major diameter

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Major diameter

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Bench Micrometer

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2. Minor diameter

16. 2. Minor diameter – Internal
Prof. M. M. Joke
2. Minor diameter – Internal
Use of Taper Parallels

17. using Thread Micrometer
3. Effective diameter –
using Thread Micrometer
Prof. M. M. Joke

18. 3. Effective diameter – using wo Wire Method E=T+P
Prof. M. M. Joke
E=T+P
Where, P is a constant, which depends upon the diameter (d) of wire and pitch (p) of the thread.
P=0.866p - d

19. 4. Pitch
Prof. M. M. Joke

20. 4. Pitch – Tool Makers Microscope
Prof. M. M. Joke

21. 4. Pitch – Thread Pitch Gauge
Prof. M. M. Joke

22. Floating Carriage Dial Micrometer – Major, Minor & Effective Diameters
Prof. M. M. Joke

23. Floating Carriage Dial Micrometer
Prof. M. M. Joke