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?
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)
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.