Drawing gears in Sketchup.

The following is a guide for designing gears in sketchup for 3D printing, CNC milling or similar. For a good introduction in general gear design see here. For an introduction to sketchup see the sketchup related links this page.

A collection of the gears seen in this page can be downloaded from the 3d warehouse.

To begin with, download the involute gear plugin and copy it to your sketchup plugin directory. This plug-in was not produced by me and all credit goes to Cadalog Inc for writing this very useful tool. Then open sketchup and choose ‘Involute Gear’ from the draw menu. From the dialogue box you are presented with three options.

  • Number of Teeth.

The number of teeth on your small gear (pinion gear)  relative to your large gear (gear wheel) will determine the gear ratio. If you desire a gear ratio of 2:1 then your gear wheel will have twice as many teeth as your pinion. However, your gear with more teeth would need need to be twice the size in order to have the same sized teeth.

By choosing an even number of teeth you have a range of different exact gear ratios. For example; 12 and 24 (1:2), 12 and 36 (1:3), 12 and 48 (1:4) ect. However, an even number of teeth will result in the same pair of teeth meeting over and over again. By having an odd number of teeth each tooth will meet a different counterpart on every rotation. This helps to distribute lubricant and reduce ware. For example, Wade’s geared extruder has 11 teeth on the pinion and 39 teeth on the gear wheel.

Try and select the highest number of teeth possible while still maintaining a printable resolution. Have no less than 12 teeth and try to avoid a gear ratio any higher than 1:6.

  • Pressure Angle.

The pressure angle effects the geometry of the gear teeth. A low pressure angle (14.5) is normally used with high number of teeth (40+) and will give a greater contact area but lead to increased noise and backlash. Source. I would recomend sticking to a pressure angle of 20. What ever pressure angle you choose, make sure it is constant among all gears used together.

  • Pitch Radius.

This is not the outermost radius of the gear (the root circle). The pitch radius is the distance from the centre of the gear to the ‘pitch point‘, the point of contact between the two gears.

As such, the outermost radius of the gear for a fixed pitch radius will change for different numbers of teeth. However, no matter the number of teeth, the ‘pitch point’ will remain constant for all gears.

The key point here is that if you want two gears to mesh well, then the pitch radius must be increase or decreased by the same ratio as your number of teeth. For example, lets say you have a small gear with 10 teeth and a pitch radius of 10mm. If you wanted a ratio of 1:3 then your large gear would need 30 teeth and pitch ratio of 30mm.

Once you are comfortable with these settings its quite simple to make a range of different gears. When you have finalised your gear design you can export the file as an STL.

Involute Gear

To create an involute gear, use the plugin as described above to first create the gear outline. The gear outline will appear at the point 0,0 so its good idea to mark the centre position before moving it. Add your centre shaft hole and then use the Push/Pull tool (hot key ‘P’)  to make the object 3d.

Helical Gear

Make sure the centre of your gear is still positioned at the point 0.0. To create a helical gear simply follow the same process as for the involute gear but with one extra step.

After you have ‘pulled’ your gear surface up to make it 3d, select only the top face of the gear and choose the rotate tool (hot key ‘Q’). With the top face still selected position the protractor over at the centre of the gear and right click. If you have an empty space for a shaft in the centre then just hold down shift while hovering the protractor over a horizontal area to lock it in that orientation. Then its just a matter of choosing your desired angle. For a single helical gear the angle used is normally 6,8,10,12,15,20 degrees. Be aware that a greater angle will result in a greater axial load (see below).

Why would you use a helical gear? They can reduce backlash, ware and noise as opposed to an involute gear. This is due to the gears meshing slowly over their length rather than all at once. However a single helical gear will result in a axial (in the direction of the shaft) load. This can be overcome by using a double helical (herringbone) gear as seen below.

Herringbone Gear (double Helical)

To make a herring bone gear follow the same processes as for the helical gear. Due to elimination of axial loading (see below) higher helical angles can be used. Eg 25,30,35,40 degrees. Select the top face of the helical gear and pull it up so that your gear is now double in height. Then use the rotate tool to rotate it back in the opposite direction as the lower half.

The advantage of the herringbone gear is that all axial forces are cancelled by the opposing helices. This allows for all the advantages of a helix gear with out any of the disadvantages. A herringbone gear will also self centre. Please note that if two herringbone gears are even slightly miss aligned and then fixed in place then they will damage each other. Its best to first fix one gear in place on its shaft while leaving the other free to move parallel to its own shaft. Then turn the fixed gear’s shaft and allow the second gear to ‘self align’  before finally fixing the second gear in place on its shaft.

More information about double helix (herringbone) gears can be found here and here.

Straight Bevel Gear

To produce a straight bevel make sure you add the shaft hole after making the bevel or else the shaft the wrong shape. Follow the same steps as for the involute gear then select the top face only. Choose the scale tool (hot key ‘S’) and while holding down Ctrl (to scale into the centre) select an outside corner and reduce the top face in size.  You will notice that as you do this you change the angle of the gear teeth.

The angle of the gear teeth is important. You can choose any angle so-long as the matching gear has a corresponding angle that together they make up 45 degrees. For example, if the teeth on one gear are at 10 degrees off the vertical then the second gear will need to have teeth that are 35 degrees off their original position.

By producing two bevel gears you can transfer mechanical power over 90 degrees.  Bevel gears can also be used to change gear ratios. The possible combinations of size and shape are endless so its best just to have a play around in sketchup to get used to it.

Internal and Planetary (Epicyclic) Gears

The involute gear plugin can also be used for creating internal gears and planetary gears. To create the external gear, first select the circle tool and starting from the origin drag it out to your desired size. This is your external gear.  Next, using the involute gear plugin produce a gear with the exact dimensions you desire for the inward facing teeth of your external gear. This will also appear at the origin. Using the pull tool, make the new gear you just created into a 3D object of any height.

The next step is the important one, select the gear ‘group’ (one click on the gear instead of two) and then right click and from the menu choose Intersect -> Intersect with model. There will be a short pause. Once done you can delete the gear group entirely and you will be left with your original circle with the outline of the gear ‘intersected’ into it. From this you can delete the centre face and pull up the outer face to give you your external gear. This can then be populated with other gears to make a planetary gear system or similar.

You can find a collecting of all these gears in one model here. If you have any suggestions, comments or corrections then by all means leave a comment.

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About Richard

I am a PhD candidate in Materials Engineering located in Melbourne, Australia.
This entry was posted in 3D Design, A Reprap Project and tagged , , , , , , , , , , , , , , , , . Bookmark the permalink.

64 Responses to Drawing gears in Sketchup.

  1. Pingback: Tweets that mention Drawing gears in Sketchup. | Capolight Electronics Projects. -- Topsy.com

  2. Pete Kuhns says:

    wow i can’t believe no one has commented yet. this is hugely helpful – I’ve been fighting Sketchup all day trying to create gears that mesh. I have been using the very-cool Gear Template Generator here:

    http://woodgears.ca/gear_cutting/template.html

    Printing to PDF, opening in Illustrator, cleaning up, then exporting as DXF. But Sketchup Pro 8 still is giving me fits. The .dxf imported gear will not act nicely ans let me push/pull it or do anything vector-y with it. A big pain in the butt.

    I’ll try the gear plug in again. Thank you so much for the helpful explanation on the plugin’s parameters. I was frustrated with those parameters because they are named something different than what you find in textbooks etc.

  3. Richard says:

    Hi Pete

    Sorry for the delay in replying, I have been on an overseas holiday for most of this month.

    I’m glad you found the post of some use. Thanks for the link to the gear template generator, that will come in handy if I ever get into laser cutting.

  4. E_Roth_3 says:

    I can’t seem to get the gears plugin to work in sketchup 8 either. Has anyone managed to get this to work with SU8?

    • Pavel says:

      @E_Roth_3 just copy gear.3.rb to program files\google sketchup 8\tools folder.

      • E_Roth_3 says:

        That solved my problem, its always a bit confusing for me whether it goes in the plugins or the tools folder…Figured I would check back in to say it IS working for me now on OS X SU8 Pro. Thanks!

  5. Jean-Marc says:

    Hi,
    Thanks for that, it’s amazing, I really enjoy it for building with my 3d printer !!
    A bit difficuly with bevel gear, I mean to find the good reduce to apply on top face, maybe you have a trick for that ..?

    Thanks
    regards

    • bobsixtyfour says:

      Use the tangent.
      The amount you reduce by is based on the angle and how tall the gear is… solve for adjacent. You plug in the angle and the “opposite” which is how tall the gear is. Then add the diameter of the smaller gear.

  6. Anton says:

    Thank you very much for writing a great plugin and explaining every thingle thing to simplest detail, including the sources. I use SU 8 and have no problems with the plugin. By the way the plugin works great in SU 8, no problems, no threats and no consernce. :)

  7. Richard says:

    I’m glad to see that many people have found the guide useful. Its quite likely you have all gotten more use out of it than I have and that doesn’t look like it will change until late November.

    As for the credit for the plug-in, that all goes to Cadalog Inc (http://www.cadalog-inc.com/). All I did was write a slightly user friendly explanation with 3D printing/CNC milling in mind.

    If any one has used this plug-in to produce an end product I would love to hear from you.

    • Anton says:

      I have used sketchup and ruby programing language a lot. and I’m planning to make a plugin that would draw differential gear, worm gear and other type of gears. This plugin that I downloaded is a great example and I can just edit it with my features.

  8. YT Sim says:

    I am using sketchup 8 on the macbook pro running Snow leopard.
    plugin give this error

    Error Loading File gear.3.rb
    undefined method `GetString’ for nil:NilClass

    Any solution for this?

    • Richard says:

      A few comments up Pavel wrote this:

      “@E_Roth_3 just copy gear.3.rb to program files\google sketchup 8\tools folder.”

      So I can only suggest that you try moving the gear.3.rb file to the tools folder in your google sketchup 8 directory.

      I’m afraid that’s about as much help as I can be.

      • YT Sim says:

        Thanks – It did not give any error message after moving to tools folder, but nothing else happen not present in the menu.

      • YT Sim says:

        Sorry – its working now it appears in the Draw menu. Thank you.

    • Anmar says:

      “Thanks – It did not give any error message after moving to tools folder, but nothing else happen not present in the menu.”
      where is the tools folder?

    • wagner says:

      Same problem here.
      Just installed Sketchup Make (eval), and gear.3.rb gives me the same error, no matter if it is installed in Tools or Plugin folder.

      Error Loading File gear.3.rb
      undefined method `GetString’ for nil:NilClass

      Any solution for that?
      Thanks.

  9. Johno says:

    Thanks for a great explanation and introduction to a fantastic plug-in.
    I haven’t had any trouble loading it or using it in Sketcup 8 except for the
    Bevel Gears. How do you know what angle you are making the gears when
    the scale tool only reads as a percentage of the original size?

  10. anthony says:

    Wow, this is extremely helpful! Thanks a lot for sharing, this will greatly help me in designing gears for my tracker projects :)

  11. MisterT says:

    The Helical Gear representation is quick and easy for illistration purposes but is not mechanicaly correct. The twist generated by standard rotation tool causes a straight geometry between gear end faces. The true geometry is curved. This can be illistrated by a multiple pull and twist operation which will still be an approximation! Hope this helps. This is a very useful plugin Thanks.

  12. jim dorey says:

    before i bother… can it be massaged to do sprockets, for chain?

  13. Thanks for a great introduction and explanation about gears…thanks for sharing it…I am also working with Steelmansgears which is a leading gear cutters manufacturer and exporter of Gear Hobs, Involute Gear Hobs, Hub Type Shaper Cutters, Shank Type Shaper Cutters, Shaving Cutters, Chamfer Hobs, Sprocket Hobs and Straight Spline Hobs in India.

  14. jd says:

    Oh my god, this is awesome. Just discovered it and now I’ll have to use it right away!

  15. Thomas Hernon says:

    I cant get gears to mesh properly, teeth of both gears contact each other instead of a tooth into root mesh! Is this a parameters issue or is it because i dont have proper spacing between the gears? I will be using SU8 allot now that I found it, Im an engineering student and have a small business that I design and build wheelchairs and handicapped equipment. Also am starting a side business linked with the other that I help inventors make their ideas come to life, my website is back2sports.net check it out and contact me if you have an idea and now means to make it work I have full machine shop in garage and can build pretty much ANYTHING! Is there any plugins or does anyone have suggestions on how to draw tube frames (like a wheelchair frame or roll cage rtc..)? Right now I draw basic shape with line and use follow me tool with circle perpendicular to the paths endpoint, seems like there should be an easier way

    • Richard says:

      Hey mate thanks for the comment.

      It sounds to me like your in need of a more serious CAD program. Sketchup is great for the basics but for more involved design work its far from optimal. Not being an engineer my self i cant be of much help in suggesting more appropriate CAD software. All i can suggest is that you go and knock on the doors (or email) your teacher/lecture/supervisor and tell then what your involved with and explain your problem. You will find that they will be glad to help you out.

      Best of luck!

      Richard.

  16. Thomas Hernon says:

    Well thanks for that but I have had solid works and autoCAD both student versions and they expired! I am currently working on raising funds for the full version of solid works (4,000 or more if I want finite elemental/stress analysis) but as of now sketchup is all I have. I know I will have to use SW for more complex designs but want to use SU for layout. What state and shape should the involute gears be in to mesh? I know about gear ratios and stuff (and am a little confused on how to choose an appropiate ratio) but do I need to have an even number of teeth on one gear and odd on the next, or both odd, or both even? If # of teeth is even then the same teeth will mesh over and over again right? (that is what I gather from reading above).

    • Richard says:

      $4,000 really is a lot to pay for software! You don’t have access to computers through your school/collage/university that have licensed copies? If not have you considered any of the open source CAD software programs? I haven’t used any of these myself so I cant make any recommendations, but I hear good things about them.

      As for gear design it goes with out saying there is a lot of information on the subject. I only scratched the surface myself when reading up on the topic before writing the post above and I cant really offer any extra knowledge as I don’t have any.

      All I can suggest is that you start reading up on the topic. There is plenty of information out on the net. I would be interested to hear how you go so do post your findings!

      Cheers.

      Richard

  17. Thomas Hernon says:

    Cool thanks, I can get them to mesh now but my pinion gear gets pushed away when I play animation. So I think I need to fix it to a point some how, I thought that linking a hinge to it would do the trick but still gets pushed away! I got out my physics book the other day and brushed up on gears and gear trains but that helped very little (i can calculate diameter and RPM of any gear but could not find a way for it to halp me in sketchup yet). I do have access to way more advanced programs but its summer and Im trying to stay away from there till semester starts cuz lord nows I spend allot of time there when it starts haha!
    Thanks for the help! I will try to let you know how it goes
    P.S. pretty much all the tutorials I have found have been crappy, the ones that would have been helpful had no sound so all I could do is watch and guess at what menus and functions they were using! Someone should make one with instructions on how to space and fix the gears and also what state and shape each gear should be in (under sketchyphysics), I would but gotta figure it out first haha

  18. Tim says:

    Hello,
    I am trying my best to get gears.3.rb to work, but I can’t seem to figure it out. I moved out all of the plugins I had and it still won’t work (thought there might be a conflict). I tried moving it to the Tools folder. Then, I changed some text on it like I found on another website. Nothing seems to work. Any help? I am using Windows 7, Sketchup 8.
    Thanks!

    Tim

  19. Mark says:

    I put the gears.3.rb in my Tools directory of SketchUp Version 8.0.4810 and the program will draw a gear, but I can’t use the Push/Pull tool to extrude it. Looks like it’s not a valid surface. Anyone else seen that or have any advice? Thanks!

  20. Thank you!! Alot :) Now i can make gears for my prototypes, and print them out on the 3d printer.

  21. Aniruddha says:

    Can we create a worm gear??

  22. Jeremy L says:

    Any chance someone can help me with the steps of adding the hole in the center of the gear before the gear is pulled into three dimensions?

    • Jim says:

      Jeremy, I selected the gear shape, right clicked and exploded it. Then I could draw a circle in the center and extrude them separately. Hope this helps.

  23. Pingback: Engranajes | Apuntes de katxarreo

  24. Parmis says:

    I can’t create the EXTERNAL gear. please help.
    thanks

  25. Rich Beck says:

    @Jeremy, The gear is created at 0,0 in Sketchup so your center is easy to find. My guess is you’re having trouble making the hole, not placing it in the center. I had the same problem until I figured out that I needed to select the group that is the gear, right click, edit, draw the circle, select the center area of the circle with your mouse, then delete it to leave a hole. You can then select your extrusion tool and make the gear as thick as you want it. When you’re done editing the component, click outside of it with the cursor tool (arrow on left top). That should do it.

  26. Rich Beck says:

    @Richard, all I can say is that this article is a fantastic help. I had a little trouble getting the plugin to showup in Sketchup 8 but once I read far enough, I found the answer to that in the comments. Your instructions have allowed me to make plastic replacements for a lasercut plywood 39 tooth gear that is part of a filament extruder on a kit I am building. The gear was cut from low quality plywood and a couple of teeth were broken when something banged it. I just designed and printed one in ABS that looks to be a perfect match for the original. Many thanks for the well written guide.

    One trick for putting the rotate tool on the center of an extruded gear with a hole down the middle is to use the tape measure to draw guides across the whole and then do the shift key, rotate tool process you describe above.

  27. Pingback: Drawing gears in Sketchup | The Deep River Railroad

  28. With havin so much content and articles do you ever run into any issues of plagorism or copyright violation?
    My site has a lot of unique content I’ve either authored myself or outsourced but it looks like a lot of it is popping it up all over the internet without my permission. Do you know any techniques to help reduce content from being ripped off? I’d
    truly appreciate it.

  29. intijk says:

    Thank you for such a useful article. At first, I want to do this in Pro/E, but there are too many steps in Pro/E. Thanks for the Sketchup version.

  30. mgiraldo says:

    Thanks for the article! Do you know if there is an equivalent plugin to create racks? I am doing a very basic rack and pinion but can’t find a guide for the rack.

    Thanks

  31. fidel says:

    excelente plug-in para generar diseños de engranajes en sketchup, alguien sabe como diseñar engranaje helicoidales( gusanos)en el mismo programa o algun plug-in

  32. conescu says:

    I put the plugin in the Contents/PlugIns folder in SketchUp 7 (Mac, free version) but it doesn’t show up anywhere. Any suggestions?

  33. karibe says:

    How can i make the rack and pinion with this, i mean the flat part, how to make matching teeth to the driving gear?

  34. Pingback: lasercut fingerjoint enclosures; pictures & code « Manifest Density

  35. JoKu says:

    I still get the error “Error loading File gear.3.rb undefined method ‘GetString’ for nil:NilClass
    I use WIn8Pro and the latest SketchUp Make V 13.0.3689
    I tried to copy the “gear” file in the folders Tools and Plugins. Neither works.
    Any idea?
    Thanks in advance

  36. michael says:

    Does not want to work in sketchup 13/make pro trial

  37. f4lkners says:

    Solution to the “Error loading File gear.3.rb undefined method ‘GetString’ for nil:NilClass” problem:
    At the bottom of gear.3.rb:
    [...]
    add_separator_to_menu($exStrings.GetString(“Draw”))
    UI.menu($exStrings.GetString(“Draw”)).add_item($exStrings.GetString(“Involute Gear”)) { Gear.dialog }
    UI.menu($exStrings.GetString(“Draw”)).add_item($exStrings.GetString(“Key Involute Gear”)) { KeyGear.dialog }
    [...]

    Remove the “$exStrings.GetString(…)” calls everywhere so the code looks like this:

    [...]
    add_separator_to_menu(“Draw”)
    UI.menu(“Draw”).add_item(“Involute Gear”) { Gear.dialog }
    UI.menu(“Draw”).add_item(“Key Involute Gear”) { KeyGear.dialog }
    [...]

    You are welcome. :)

  38. fnaeem786 says:

    Thanks f4lkners, sure made my day!

  39. Doorcontrolgeek says:

    Thanks f4lkners, you made my day also. The Gears plug-in would not work, but with your recommended changes, it does! Thank you so much for sharing!

  40. MakeATrainDrive says:

    Thank you for solution to launch error. Download still has the error in it as of today though.

  41. Keith Mancini says:

    I am trying to make a Helical gear, and when I rotate the top surface the center of the gear “squishes” for lack of a better word. Any idea how to prevent that? Thanks.

  42. Peter Buch says:

    Hi Richard,

    thanks for your great contribution. It’s really helpful.

    There is still a problem in making bevel gears. A correct bevel gear must be constructed using spherical geometry. The construction you describe starts from the tangent plane. It must be observed that the projection to the tangent plane changes the pressure angle. I made some calculations and found:

    tan(pressure angle on the plane) = tan(pressure angle on the sphere) / cos(tooth-axis angle)

    The pressure angle on the sphere is the “real” one. The pressure angle on the tangent plane is greater, and has to be used when starting the construction from that plane.

    In a 1:1 bevel gear, where both half cone opening angles are equal (= 45°), this won’t matter, as the pressure angles will match. In my case, I need a 23:19 gear. The two gear wheels have tooth-axis angles of 50° and 40°, and a common pressure angle of 20° has projections of 30° and 25° on the respective tangent planes.

    And now the problem: The involute gear plug-in offers only 3 distinct values (14.5°, 20°, 25°) for the pressure angle. There is no way to choose user-defined values, in order to make matching bevel gears. The mismatch get the worse the more the ratio differs from 1:1.

    Do you or anybody know a solution to that?

    Peter

  43. Rossi Mario says:

    hi. how can i make a rack?

    i need to create a planetery gear with four pignons that move four rack.

    thanks for your Attention

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  45. efrem says:

    Thanks a lot for this post! Thank a lot to f4lkners too for his hint on how to get the plugin working!

  46. Gasser says:

    Thank-you f4lkners and Capolight. I used this to make a replacement gear on my lathe.

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