Difference between spur gear and helical gear

Spur and helical both of this two are different types of mechanical gears but there are fundamental difference according to there design and make more suitable in there given respective task.

What is spur gear?

Spur gears are also known as straight-cut gears consists of a cylinder or disk with radially projected teeth and the edge of each tooth is straight and aligned parallel to the axis of rotation. 

What is helical gear?

Helical gears are one type of cylindrical gears the teeth are cut at an angle to the face of the gear. It is an improved version of the spur gear. 

Let us have a deep insight into the compassion and difference between both gears. 

Difference between the spur and helical gear : 

  • Spur gear there is no helix angle while helical gear has helix angle.
  • Contact between teeth of two meshing gears occurs suddenly in case of spur gear whereas gradually occurs in helical gear. 
  • For high-speed transmission, helical gears are used as there is less noise than spur gears.
  • Helical gear has a higher contact ratio than spur gears and they operate smoother and quieter than spur gears.
  • Helical gear has longer teeth than spur gears and has a higher load-carrying capacity. 
  • Straight tooth gear used to transmit power in spur gear while helical gear has teeth inclined to the axis.
  • In spur gear, there is a negligible axial thrust present between shafts while in a helical gear higher axial thrust may be present. 
  • Spur gears are more efficient than helical gears.
  • The cost of manufacturing spur gear is less than that of the helical gear.
  • Helical gears are more durable than spur gears.
  • A spur gear is suitable for the velocity ratio of 1:1 to 1:3 and helical gear is suitable for the velocity ratio of 1:1 to 1:5.
  • Teeth of spur gear can be cut easily as it required only two-dimensional motion while making teeth for helical gear comparatively difficult as it required three-dimensional motion. 
The similarity between the spur and helical gear : 
  • Both are suitable for transmission of power and motion between parallel shafts only not used for the non-parallel shafts. 
  • Both gears can provide a positive drive. 
  • Both are suitable for a smaller distance of power transmission not above 0.5m.
  • In both gears, there is no flexible element exist between two gears.  
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