This presentation was made by me to supplement classroom lecture on Gear Cutting technology as part of the Machine Shop technology module for IV Semester of DME and DAE students of K Scheme. Useful for Polytechnic College Students of India.
71. Helical gear tooth proportions Where Normal Module “Mn” = m cos α m = Module α = Helix angle S.No Name of tooth element Tooth proportions in terms of normal module with 20° pressure angle 1. Pitch diameter Zm 2. Addendum Mn 3. Dedendum 1.25 Mn 4. Tooth depth 2.25 Mn 5. Outside diameter Zm + 2 Mn 6. Normal tooth thickness 1.5708 Mn
99. Bevel gear tooth proportions S.No Name of tooth element Tooth proportions for 20° pressure angle Symbol 1. Pitch diameter Zm d 2. Addendum (large end) 1 m ha 3. Dedendum (large end) 1.25 m hd 4. Tooth depth (large end) 2.25 m h 5. Tooth thickness (large end) 1.5708 m s 6. Circular pitch π m p
100. Bevel gear elements and angles S.No Name of tooth element Symbol Formula 1. Face width b b = 0.5 to 0.33 R 2. Cone distance R R = 0.5 / sin β 3. Addendum angle θa tan θa = ha / R 4. Dedendum angle θ d tan θ d = hd / R 5. Pitch cone angle β Sin β = 0.5 d / R
112. Gear Generating Process Gear generation is based on the fact that “any two involute gears of the same module will mesh together” Gear teeth are generated in the gear blank because of the relative rolling motion of the cutter and the blank. One of the mating gears in a cutter which reciprocates and also rotates as a mating gear. Accurate tooth profile is generated in this process.