Keys.pptx

Machine Drawing, Keys: Parallel key, Taper key, Feather key, Gib-head key and Woodruff key

1. Department of Robotics & Automation JSS Academy of Technical Education, Bangalore-560060 Robotics System Drawing & Standards (Course Code:21RA35 )

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. Module 3 Keys: Parallel key, Taper key, Feather key, Gib-head key and Woodruff key

5. A Key is a machine elements used to connect a rotating machine element to a shaft. Keys are used to prevent relative motion between shaft & hub. A Keyway is a slot in a shaft & hub of the pully to accommodate a key. Used for transmitting the torque & as temporary fasteners and are subjected to crushing and shearing stresses. Introduction to Keys

6. Commonly employed method to connect a shaft and a machine part is to drive a small piece of meta l known as KEY . To drive the key, axial grooves are cut both in the shaft end the part mounted on it. The groove in the shaft is called the “ KEY CUT ” and the groove in the part is called the “ KEYWAY ”.

7. Keys are classified into three types , Taper keys Parallel keys Special purpose keys Introduction to Keys

8. Taper key Sunk Taper Key A sunk taper key is of rectangular or square cross section of uniform width having its bottom surface straight and top surface tapered. If D is the diameter of the shaft in mm W = Width of the key T = Thickness of the key W = 0.25D+2mm T = 0.66W Standard taper = 1:100 Sunk Taper key Proportions Take diameter = 50 mm and Length = 100 mm

9. If D = 50 mm and Length = 100 mm W = Width of the key T = Thickness of the key W = 0.25D+2mm = 0.25 x 60+2 = 14.5 mm T = 0.66W = 0.66 x 14.5 = 9.57 Standard taper = 1:100 Indicate only proportions on the drawing and show the calculations Sunk Taper Key Proportions

10. Gib Head key If D is the diameter of the shaft, then, Width of key, W = 0.25 D + 2 mm Thickness of key, T = 0.67 W (at the thicker end) Standard taper = 1:100 Height of head, h = 1.75 T Width of head, b = 1.5 T Gib Head Key Proportions

11. Gib Head key If D = 50 mm and Length = 100 mm Width of key, W = 0.25 D + 2 mm = 0.25 x 50 + 2 = 14.5 mm Thickness of key, T = 0.67 W (at the thicker end) = 0.67 x 14.5 = 9.715 mm Standard taper = 1:100 Height of head, h = 1.75 T = 1.75 x 9.715 = 17.001 mm Width of head, b = 1.5 T = 14.57 mm Gib head angle = 45 deg Indicate only proportions on the drawing and show the calculations

12. Parallel key or Feather Key A parallel or feather key is a sunk key, uniform in width and thickness as well. These keys are used when the parts (gears, clutches, etc.) mounted are required to slide along the shaft; permitting relative axial movement.

13. If D = 50 mm, Width of key, W = 0.25 D + 2 mm = 14.5 mm Thickness of key, T = 0.66 W = 9.57 mm Parallel key or Feather Key Take diameter = 50 mm and Length = 100 mm Indicate only proportions on the drawing and show the calculations

14. It is a sunk key, in the form of a segment of a circular disc of uniform thickness. Woodruff key is mainly used on tapered shafts of machine tools and automobiles. The following are the proportions of woodruff keys: If D is the diameter of the shaft, Thickness of key, W = 0.25 D Diameter of key, d = 3 W Height of key, T = 1.35 W Woodruff key Woodruff key Proportions

15. If D is the diameter of the shaft, Thickness of key, W = 0.25 D = 0.25 x 50 = 12.5 mm Diameter of key, d = 3 W = 3 x 12.5 = 37.5 Height of key, T = 1.35 W = 1.35 x 12.5 = 16.87 mm Woodruff key Woodruff key Proportions Take diameter = 50 mm Indicate only proportions on the drawing and show the calculations

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