I'm working on a LEGO compatible motor system that will be largely 3D printed. I want the connectors to fit standard LEGO axles, but I haven't been able to find the dimensions online, and I don't have any on me to measure. What are the dimensions of the cross-section of a LEGO axle. Is there a difference in size between the plus-shaped hole for and axle and the axle itself?

  • Do these have enough dimension details? LEGO Technic Axles
    – DrZoo
    Commented Nov 20, 2017 at 16:05
  • No, the length is easy to find, but I need the dimensions of the cross section Commented Nov 20, 2017 at 17:33
  • Specifically I need most the width of the ridges on the axle Commented Nov 20, 2017 at 17:34
  • Gotcha. The dimensions L x 0.4cm x 0.4cm is easy to understand, but do you have any idea what stud dimensions : 0.33 means?
    – DrZoo
    Commented Nov 20, 2017 at 17:51
  • It appears to be relative to a normal brick, for example the standard brick has stud dimensions 2 x 4 x 1 Commented Nov 21, 2017 at 2:10

1 Answer 1


I found CAD files for LEGO technic axles here: https://grabcad.com/library/lego-technic-axles-1 and some gears which have holes for technic axles here: https://grabcad.com/library/lego-technic-gears-1

Using their online viewer I found the following dimensions (Which are a little inaccurate due to the limits of their online viewers tools. For more accurate and detailed dimensions download a copy of the CAD files)

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This would seem to indicate (if accurate) an interference fit between the outsides of the axles and the holes (i.e. the hole is slightly smaller) which could be accurate as axles are usually tight.

Someone should also probably measure actual LEGO parts with some calipers for confirmation on these dimensions.

  • This is great! Thanks. I'm traveling for thanksgiving, and I'll take my calipers to measure some actual parts. I'll comment with results. Commented Nov 22, 2017 at 16:26
  • my caliper says 4.68 rather than 4.78 for cross width, and 1.83 vs 1.79 for cross arm width.
    – jumpjack
    Commented Feb 16 at 19:05

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