We recently installed media (blackout) shades for our skylights, so we can watch movies when the sun is out. Our family room ceiling is quite high, so the pole and hook designed to open and close the new shades is too short. I designed this replacement cap and hook to fit a longer pole.
The two parts of the thing are hook.stl and cap.stl. The FreeCAD design file is WindowShadeOpener.FCStd.
There are two parts to print: the cap and the hook. Print the cap with the open end facing up. Print the hook with the chamfered (beveled) side down.
I printed in PLA.
Glue the hook to the cap: put glue on the hook everywhere it will touch the cap, then position the hook so the little tab at its bottom (circled in an image above) fits into the little slot in the cap (also circled in that image).
I used E6000 craft adhesive, which takes 1-3 days to become strong enough to use, to glue the parts together.
I started by measuring the thread in the pole I wanted this part to screw onto, then designing a matching thread and cylindrical cap.
I tested how well the threads matched by subtracting a pie-shaped slice from the cylinder, then printing that. See my post about that process, at https://bluepapertech.com/3d-printing/designing-3d-printed-threads-to-match-existing-parts/
I tried two different designs for connecting the hook to the cap. The first design was just a hole that the hook pressed into. That design didn't work: the glued hook just pulled right out of the hole. The second design is what you see here: the hook glues into a long channel in the cap, and a matching little tab and slot help the hook stay in place when it's pulled straight up.
I modeled the length and angle of the hook to match the original part.
I chose an angled, sort of triangular, thread outline so the thread would match the square-outline thread of the pole, but would print without support.
The chamfer on the cap and hook are designed to compensate for overextrusion of the first few layers, so the hook fits accurately into the cap's channel.
I designed the hook as a separate part so it's strong enough. If I had instead made the hook print vertically, it would snap off because 3D prints are relatively weak in the Z direction (up/down).