Sorry in advance for the long post. I think some people are probably curious about the overall build process, but I should probably get a blog and just post a link
For Christmas, one of my friends got me a little crossbow pistol. I felt like it really needed a rail on it to hold the bolts it came with and decided to design something that would attach under it. The length of it had oval shaped holes and I decided to use those. You can see them in this photo:
Those oval shapes were a complete PITA to attempt to measure with nothing but calipers (I looked around on Amazon for pin gauges today that would have made the job easier ). I decided to use the first and second slots near the front and did some test fit pieces to make sure I could get it correct:
My first attempt on the first one was really close. The second one took a lot more effort:
Once I felt like I had the slot dimensions good, I CAD’d up some pieces in FreeCAD (I like using it when I’m not sure if just “free as in beer” is good enough). The front pieces had a circular pocket for the head of the M3 screws while the back pieces had a hexagonal pocket for the nuts to fit into:
I then designed a rail (the piece that actually holds the bolts) to go between them:
A little time in “Prusa Control” (Slic3r) to generate G-Code:
The printed pieces looked like this (I pressed the nuts in with pliers. I probably should buy a small press or use a vice next time):
This shows the pieces (minus the rail that goes between them and the screws in place):
And finally the finished product with it in use (bolts attached):
Next time I might go with just slots to push the nuts through instead of the hex holes for nuts which were a PITA to clean out with support material due to printing orientation. It also makes me consider getting a multimaterial unit (MMU) and investigate the support filaments that dissolve in water.
I might try this again later with 3 total pieces (combining front and back pieces), but I didn’t want to worry about the exact length of that. I also probably need to fillet a few more sides where possible for comfort reasons.