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1) Red: Danger,Hot 2) Orange: Possible Orange 3) Green : Safe 4) Blue: Cold

Keys are classified on the basis of shape and application of keys.………………are 1) Sunk Key : a) Rectangular sunk key b) square sunk key c) Gib head key d) feather key e) Woodruff key 2) Saddle key a) Flat saddle key b) hollow saddle key 3) Round key 4) Splines …………………: 1) Sunk Key : used for heavy duty application a) Rectangular sunk key : for preventing rotation of gears and pulleys on shaft b) Gib headed key: used where key to be removed frequently.

 i) Fe E 230 : Steel with min.Yield strength of 230N/mm2 ii ) X20Cr 18 Ni 2:Specification: It is ALLOY STEEL having Carbon 0.20% ,Chromium 18% and Nickel 2%  iii )35 C 8 : steel with 0.35% carbon & 0.8% Manganese.

iv) 40 Ni 2 Cr 1 Mo 20 :Alloy Steel having 0.4% carbon,0.5% Nickel, 0.25% chromium,2.8% Molybdenum.

Following are the three types of screw threads mostly used for power screws: 1. Square thread. 2. Acme threads 3.trapezoidal thread. 3. Buttress thread