This is my first project so please share your feedback. I'm new in design and 3d printing but I was in a desperate need to fix some parts of my garden swing. You may need a 12mm bolt to put parts together.
credit for the Hirth Spline: https://grabcad.com/library/hirth-spline-1
PETG and support (might be needed). I have printed myself with 0.3 and 40% infil but you may chnage these.
The author hasn't provided the model origin yet.