Geometry of involute gears

This article provides answers to the following questions, among others:

  • How is the shape of the tooth of an involute gear obtained?
  • What is an involute? 
  • How is an involute of circle constructed?
  • What is the base pitch?
  • What is described by the module?
  • How is the standard reference pitch diameter determined?
  • How does the standard pressure angle influence the flank shape?
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Meshing of involute gears

This article provides answers to the following questions, among others:

  • What is the line of action of two meshing gears?
  • How is the position of the line of action determined?
  • What is the line of contact and how is it determined?
  • What is the pressure angle?
  • What determines the standard pressure angle?
  • What ist the base pitch?
  • What statement does the contact ratio provide?
  • How does the base pitch and the contact ratio change when the centre distance is increased?
  • How is the pitch point defined?
  • How do the operating pitch circles change when the centre distance is changed?
  • What is the fundamental law of gearing?
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Rack

This article provides answers to the following questions, among others:

  • How is the line of action and the line of contact determined for racks?
  • How does the position of the pitch point change when the distance increases?
  • Why does the transmission ratio always remain constant even if the distance changes?
  • How can the standard reference pitch circle of a gear be defined using a rack?
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Gear cutting

This article provides answers to the following questions, among others:

  • How are gears manufactured?
  • What are the advantages and disadvantages of gear hobbing?
  • What are the advantages of gear shaping with a pinion-shaped cutter compared to planing with a rack type cutter?
  • What is the basic principle of hobbing, shaping and planning?
  • What are the advantages and disadvantages of form cutting compared to hobbing, shaping and planning?
  • How is broaching used for gear manufacturing?
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Undercut

This article provides answers to the following questions, among others:

  • What is an undercut?
  • How does undercutting occur during gear hobbing?
  • What effects does an undercut have on the load capacity of a gear and on the line of action?
  • Why does an undercut have to be present in gears with a small number of teeth for functional reasons?
  • How can the minimum number of teeth be determined so that no undercut occurs?
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Profile shift

This article provides answers to the following questions, among others:

  • What is a profile shift?
  • What is a profile shift used for?
  • Why can the flank load-bearing capacity be increased by a profile shift?
  • Why does neither the reference pitch circle diameter nor the base circle diameter change with a profile shift?
  • What is the profile shift coefficient?
  • Why is it necessary to shorten the tip circle with a profile shift when the number of teeth is small?
  • How is the profile shift coefficient required to avoid an undercut calculated?
  • What are the advantages of profile-shifted gears?
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Calculation of involute gears

This article provides answers to the following questions, among others:

  • center distance
  • tip shortening
  • sum of the profile shift coefficients to obtain a certain center distance
  • operating pressure angle
  • transmission ratio
  • standard reference pitch circle
  • operating pitch circle
  • tip, root and base circle diameter
  • tip tooth clearance
  • (tip) tooth thickness
  • contact ratio
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