Thread Forms.pptx

Thread terminology, sectional views of threads. ISO Metric (Internal & External), BSW (Internal & External), Square and Acme, Sellers thread, American Standard thread.

1. Department of Mechanical Engineering JSS Academy of Technical Education, Bangalore-560060 Computer Aided Machine Drawing (Course Code:18ME46A )

2. TEXT BOOKS Machine Drawing, K R Gopala Krishna, Subhash Publication, 2005. Machine Drawing, N D Bhat & V M Panchal, Charoratar publishing house, 2005. Further Reference: National Programme on Technology Enhanced Learning ( NPTEL ) https://nptel.ac.in/courses/112103019/

3. To impart knowledge of thread forms , fasteners , keys, joints and couplings . Course Learning Objectives

4. Sheet No. 2 Thread terminology, sectional views of threads. ISO Metric (Internal & External), BSW (Internal & External), Square and Acme, Sellers thread , American Standard thread.

5. Screw: A screw is a cylindrical rod , with a helical groove cut on it. Screw threads are used to fasten the parts together . Temporary fasteners Sheet No.2 Thread Forms

6. Thread Terminology Sheet No.2 Thread Forms

7. Thread form choice depends on;   What it will be used for Length of engagement Load

8. Right-handed and left-handed threads The helix (or spiral) of a thread can be designed to be either right-handed or left-handed. Majority of threads are right-handed and follow the right-hand grip rule. Right-hand grip rule : When a thread is engaged in a connection, it moves upward if rotated in the direction of the right hand. The letters “LH” in a thread spec stand for a left-handed thread.

9. Basic Profiles / Forms of Threads Two basic profiles / forms of screw threads are; V thread Square thread

10. Standard forms of V Threads Whitworth Thread – British Standard (BS) (55°) Sellers thread - American Standard (60°) ISO Thread (Unified Thread) – Indian Standard (60°) Square Thread – Indian Standard Standard forms of Square Threads Modified forms of Square Threads Acme Thread (29°)

11. Draw to scale 1:1, the standard profile of a BSW thread taking P = 50 mm. Show at least three threads. 1. Whitworth Thread – British Standard (BS) H = 0.96 P

12. Draw to scale 1:1, the standard profile of a Sellers thread taking P = 30 mm. Show at least three threads. 2. Sellers Thread – American Standard H = 0.86 P

13. Draw to scale 1:1, the standard profile of a ISO thread (both internal & external) taking P = 50 mm. Show at least three threads 3. ISO Thread – (Internal & External) H = 0.86 P

14. Draw to scale 1:1, the standard profile of a ISO thread (both internal & external) taking P = 50 mm. Show at least three threads 3. ISO Thread – (Internal & External) H = 0.86 P

15. Draw to scale 1:1, the standard profile of a Square thread, taking P = 50 mm. Show at least three threads 4. Square Thread – (Internal & External) H = 0.5 P

16. Draw to scale 1:1, the standard profile of a Acme thread, taking P = 50 mm. Show at least three threads 5. Acme Thread – (Internal & External) H = 0.5 P + 0.25 mm

17. End of Sheet No. 2