ScrewBall

After trying numerous methods to get the parts to print correctly, I determined that the unusual printing position produced the best overall smooth surfaces. Print 3 identical parts. Scaling not recommended without tolerance re-design. Use the slowest, thinnest layers you can tolerate. Support and orientation are critical. Stick with the orientation I have here unless you just can't get a good print without reorienting the parts.
I used .2mm layers of Prusament PLA on a Prusa i3 MK3s. Use .15mm layers if you can take the extra time to print. I will include the gcode I used for that printer. See the picture of the part orientation on the print bed and the support I used. The support is for 45 deg. overhangs, 2 raft layers. I used 3 bottom, top and side layers.
Cleanup: make sure the middle of the inside curve line, as well as all interior surfaces, are cleaned up to make sure the parts will slide together well.

Assemble. Easy so I will not say more.

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