Answers.Body: <p><strong>Quick answer:</strong> LEGO gear module is 1 (metric).</p>
  
  <p>See Section 3.4 at this link: <a href="http://bdml.stanford.edu/Main/CrawlerNotes" rel="noreferrer">http://bdml.stanford.edu/Main/CrawlerNotes</a></p>
  
  <p>The consensus seems to be the following:</p>
  
  <ul>
  <li>Lego gears have a metric module of 1, which is the same as a pitch of 25.4 teeth per inch of diameter.</li>
  <li>Pressure angle is likely to be about 20 degrees. (This is the most common angle with modern gearing.)</li>
  <li>Face width is approximately 1/8 inch. Perhaps more precisely: b = 0.14 inches? - according to a measurement somebody took with calipers in 2011. But note that not all LEGO gears have the full face width. In particular, the crown gears (LEGO's version of bevel gears) do not have a full face width.</li>
  </ul>
  
  <p>From <a href="http://orionrobots.co.uk/Lego+Specifications" rel="noreferrer">http://orionrobots.co.uk/Lego+Specifications</a>: </p>
  
  <blockquote>
    <p>In the Lego system, technic gears have a ratio that the number of
    teeth are 8 times the diameter, or 16 times the radius in stud pitch.
    Conveniently - the number of studs, and Diameter in Millimeters seem
    to be the same. Note: one "stud" is 8mm. So: 16 tooth gear is 2 studs
    = 16mm => diametral pitch = 1mm.</p>
  </blockquote>
  
  <p>Also, I have personally 3D printed custom gears with a pressure angle of 20 degrees and a module of 1, and these meshed perfectly with my other LEGO gears.</p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-07-23T17:08:16.303Z
Answers.Text: How did you know that my next question was going to be what the pressure angle is?
Answers.UserDisplayName: user2813274
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-10-24T10:27:01.200Z
Answers.Text: How interesting that when trying to find more information about this, I end up back at the answer - referring back to my Orionrobots site. Does anyone have an up-to-date link for the Stanford document there?
Answers.UserDisplayName: Danny Staple
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-07-19T20:51:43.587Z
Answers.LastActivityDate: 2015-07-20T13:12:53.660Z
Answers.LastEditDate: 2015-07-20T13:12:53.660Z
Answers.UserDisplayName: Etienne Ackermann
Body: <blockquote>
    <p>Module, m this indicates the tooth size and is the number of mm of
    pitch circle diameter (p.c.d.) per tooth. For gears to mesh, their
    modules must be equal. Gear ISO standards and design methods are now
    normally based on the module. EG a gear of module 3 has 16 teeth, its
    pitch circle diameter is: 3 x 16 = 48 mm.</p>
  </blockquote>
  
  <p>Source: <a href="http://www.tech.plymouth.ac.uk/sme/desnotes/gears/nomen1.htm]" rel="noreferrer">Plymouth University. Gear Tooth Nomenclature.</a></p>
  
  <p>I am curious as to which non-LEGO gears will mesh well with LEGO gears, but this is one of the more important numbers as far as figuring that out, yet I don't see the concrete number mentioned in any of the various LEGO gear descriptions/tutorials that show up when I search for it</p>
  
  <p>To be very clear, all I am looking for is either single number, or an answer of "LEGO doesn't follow the mentioned Gear ISO standards". </p>
  
Tags: <technic><terminology><gears>
Title: What is the "Module" of a LEGO gear?
UserDisplayName: user2813274
ThreadText: # What is the "Module" of a LEGO gear?
  
  (Asked by: username_0 on 2015-07-18)
  
  > Module, m this indicates the tooth size and is the number of mm of
  > pitch circle diameter (p.c.d.) per tooth. For gears to mesh, their
  > modules must be equal. Gear ISO standards and design methods are now
  > normally based on the module. EG a gear of module 3 has 16 teeth, its
  > pitch circle diameter is: 3 x 16 = 48 mm.
  
  Source: [Plymouth University. Gear Tooth Nomenclature.](http://www.tech.plymouth.ac.uk/sme/desnotes/gears/nomen1.htm])
  
  I am curious as to which non-LEGO gears will mesh well with LEGO gears, but this is one of the more important numbers as far as figuring that out, yet I don't see the concrete number mentioned in any of the various LEGO gear descriptions/tutorials that show up when I search for it
  
  To be very clear, all I am looking for is either single number, or an answer of "LEGO doesn't follow the mentioned Gear ISO standards".
  
  **Tags:** technic, terminology, gears
  
  ---
  
  ## 1 answers
  
  ### Answer by username_1 on 2015-07-19. Score: 13 | Accepted answer
  
  **Quick answer:** LEGO gear module is 1 (metric).
  
  See Section 3.4 at this link: <http://bdml.stanford.edu/Main/CrawlerNotes>
  
  The consensus seems to be the following:
  
  * Lego gears have a metric module of 1, which is the same as a pitch of 25.4 teeth per inch of diameter.
  * Pressure angle is likely to be about 20 degrees. (This is the most common angle with modern gearing.)
  * Face width is approximately 1/8 inch. Perhaps more precisely: b = 0.14 inches? - according to a measurement somebody took with calipers in 2011. But note that not all LEGO gears have the full face width. In particular, the crown gears (LEGO's version of bevel gears) do not have a full face width.
  
  From <http://orionrobots.co.uk/Lego+Specifications>:
  
  > In the Lego system, technic gears have a ratio that the number of
  > teeth are 8 times the diameter, or 16 times the radius in stud pitch.
  > Conveniently - the number of studs, and Diameter in Millimeters seem
  > to be the same. Note: one "stud" is 8mm. So: 16 tooth gear is 2 studs
  > = 16mm => diametral pitch = 1mm.
  
  Also, I have personally 3D printed custom gears with a pressure angle of 20 degrees and a module of 1, and these meshed perfectly with my other LEGO gears.
  
  > **Comments:**
  > **username_0**: How did you know that my next question was going to be what the pressure angle is?  
  > **username_2**: How interesting that when trying to find more information about this, I end up back at the answer - referring back to my Orionrobots site. Does anyone have an up-to-date link for the Stanford document there?  
  
  ---
  
  