Online Involute Spur Gear Builder v2

Version 2.0 of my online involute spur builder is available now: Online Involute Spur Gear Builder v2. It is a complete rewrite of version 1 which was introduced 2014 (part1, part 2).

Version 2 creates higher quality output without ragged edges at higher speed. Like before, undercuts as needed for small tooth counts are correctly handled; clearance, backlash, and profile shift are fully supported.

As an extreme case the image on the left shows a 12 tooth gear meshing with a 5 tooth pinion (tool link). Notice the extent of the undercut. The image on the right (tool link) shows the same gears but this time with profile shift applied. The profile shift considerably strengthens the pinion gear teeth.

Without profile shift Involute gears with undercut and profile shift.

The key differences of v2 compared to v1 are:

  • Modern SVG output
  • Higher quality output (no ragged edges) without excessive segment counts. No more need to fiddle with quality parameters.
  • Significantly faster than v1 at any acceptable quality levels
  • Parameters are automatically injected in the URL; i.e., the URL fully specifies the output and can be shared with others.
  • Corrected internal gear generation (e.g., clearance is properly applied)

In case you are interested in how the gear shapes are created, the first post that introduced version 1 is a good start. Then this pdf document provides more detail about how v2 accomplishes the smooth curves that v1 struggled with. Internal gears are particularly challenging in this regard. Here is just a teaser:

Internal Gear Shape Creation

30 thoughts on “Online Involute Spur Gear Builder v2”

  1. Thank you for developing such a useful tool , I have used it to design spur gears for 3D printing. I have found that it produces an error where the undercut meets the dedendum circle – not a major issue and easy to work around in my CAD package. If you’d like me to email you details/screenshots please do let me know?

    Thanks again, Chris

    1. Chris, thank you very much for the screenshots that you emailed me. The undercut meeting the dedendum cycle does not exist in the svg output which uses circles and arcs. It was introduced in the conversion from svg to dxf that you used (dxf breaks up circles and arcs into line segments).

      However, the other problem that you exposed (small section of the gear path reversing direction before continuing again in the right direction) was a bug in my tool. I just published an update that fixes this.

      Thanks again!

  2. What a super generator, thanks so much – it certainly solved the issue of compatibility between Mac OS and Windows. One nice to have would be the option of ‘Spokes’ – is there any chance?

    Thanks again!

    1. Thank you for the kind words. Sorry, but I don’t intend to add support for spokes. There are just too many possible options. But more importantly, creating custom spokes it easily done in either CAD programs or vector graphics programs after importing the generated svg output. As a concrete example, the free open source Inkscape software is a very powerful tool specifically for editing svg.

  3. Thanks for an excellent gear generator, you must have put a lot of effort into it. I am trying to generate some gears with a pressure angle of 14.5 degrees.To check the results I have created a rack which should have the flank angle equal t o the pressure angle. When I input 14.5 degrees, I get a rack angle of approximately 14.06 degrees. When I input 15 degrees I get a result very close to 14.5 degrees. Is this an issue with conversion from SVG to DXF via Inkscape? If so, would it be possible for you to output DXF format data? Thanks again for a powerful, easy to use tool.

    1. Hi Jack, thanks for your feedback. You discovered a bug in my code. Thanks to your detailed description I was able to quickly find and fix it. It affected all three modes (regular gear, internal gear, and rack). The fixed version is now live. Please try again.

      1. Hi Rainer. Superb!. Autocad now reports 14.50000382 degrees for the 14.5 degree pressure angle. I think that is close enough!! 😉 Thank you for the prompt reply and rapid update. I’m planning to 3D print some unusual ratio change gears for my Myford lathe and now I’m sure they will mesh well with the existing originals. Thanks again for a well thought out tool. Cheers.

  4. When attempting to open involute_gear_30_to_8.svg, Rhino 5 responds with: “File type not supported by Rhinoceros (Rhino 5).
    Can you help?

    1. Hi David, Rhino 7 seven does support svg but I am not sure that formats Rhino 5 supports. I would suggest that you install the free SVG editor and use it to load your involute_gear_30_to_8.svg file. Once loaded you can then use Inkscape to export the graphics in various formats. One common option is the dxf format.

      1. Hello again Dr Hessmer, I downloaded the Win_10_64bit inkscape, installed and ran it. Then I loaded the SVG and proceeded to export it, however the only file format available was PNG. What am I missing?

      2. Dr. Hessmer, I figured out what I was missing. This time I chose to use “Save As” instead of “Export” and voilà! The full complement of file formats appeared.

      3. do you think you will ever port this code over to python for use with cadquery? it would be very useful to have a parametric function for spur gears in cadquery. This could enable interesting paremetric designs where the gears could change with other variables in the part/assembly.

  5. SVG is good. Specifying a single tooth profile in comma delimited ascii is better (as an option), since it is both more compact and in the case of a rack, can be extended without difficulty.

    As to the SVG option, adding an internal comment specifying the center of each gear would also be helpful.

  6. Hi i realy like your gear program. I have one problem. I would like to use it on my makeblock lasercutter for a school project. Unfortunally I can’t seem to get rid of the bleu center lines I tried Inkscape but I cant sellect them. My cutterprogram sees it as a cut line. can you advice me how to delete the bleu lines?

    1. Hi Gerrit,

      The objects are grouped together. You can ungroup them in Inkscape (menu Object / Ungroup). The first ‘ungroup’ will separate the two gears from each other. Then you need to select each gear again, and ungroup it. Once done you can delete the blue lines.

  7. Dear Rainer,

    I have successfully used your excellent tool for 3D-printing gears for my radio control earthmovers. I pair the PLA gears with bought-in metal pinions, which works really well.
    For my newest model, I want to use a large hollow/internal gear and I am very confused – maybe you can shed some light on this – I hope I’m not wasting your time!

    When using the example linked below, it seems the pinion and internal gear lines clash. When going to a smaller pinion (I plan to use 9 teeth), it becomes more and more obvious, which indicates that it is an issue of undercut and profile shift? But I think the internal gear’s teeth are malformed, they seem to have a “hump” at their tips, which looks wrong to me and seems different to the profile shown on GearGenerator or what the following paper describes as a “standard involute” profile for internal gears:

    Here is the link to your gear builder with the problematic settings:

    I then read up on the issues of profile shift with internal gears at and then adjusted the gears with a lot of profile shift, giving this “hump”-less and no-interference result in your gear builder:

    However, this looks totally different than either the metal pinion I bought or the GearGenerator gears, where the pinion looks much more like the one I bought. So I am really confused!,1400,25,1,1,1,12461.200000004841,2,1,107,107,1,20,-90,1,0,0,0,0,0,9,9,1,20,-50,0,0,0,0,0,0,3,-132

    Sorry for such a long-winded question!

    Best wishes

  8. Hi Jens,

    Thank you very much for the detailed analysis and the links. This is very useful. You are absolute correct. This is a bug in my gear generator. My current assumption is that I am not rolling out enough of the tooth profile and consequently fail to ‘cut off’ enough material from the ring gear.

    Unfortunately I don’t have time to jump at this right away. So I can’t promise yet when this will be fixed.

    1. No problem Rainer, glad it was helpful and thank you for looking into it 🙂
      For now, I have used Dr Jörg Janssen’s OpenSCAD library “Getriebe.scad” to generate the internal gear.

      Best wishes

  9. Hi i realy like your gear program. I have one problem. I would like to use it on my makeblock lasercutter for a school project. Danfoss Transmitter 060G0077 Unfortunally I can’t seem to get rid of the bleu center lines I tried Inkscape but I cant sellect them. My cutterprogram sees it as a cut line. can you advice me how to delete the bleu lines?

    1. Hi, the SVG output uses grouping. To delete the blue helper lines, open the output in Inkscape, select the gears and then ungroup (menu Object / Ungroup). This breaks up the top level group.

      Now select one of the gears and ungroup again. Now you can select the blue lines of this gear and delete them.

      Finally follow the same steps for the second gear.

  10. Dear Rainer,

    Thank you very much for this useful tool. I am researching internal gears and just wanted to ask you if there is a mathematical guide for your internal gear implementation?

    Thank you.

  11. Hello Dr. Hessmer,
    I very much appreciate your online program. I use it often when generating gear patterns for my 3D printing projects.

    I do have one question,
    Did you intend to leave the outer gear diameter (for an external gear, (-)tooth count) as the larger diameter of the graphic instead of the diameter of the outer tooth line?


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