Update: Someone pointed out that the nut file was hosed. I re-uploaded it.
This is the second version of the Carabiner I made a little while ago. I made the other one with Nylon in mind as the print material. Nylon is really strong but it's a pain in the butt to print so I wanted to make one that could hold my weight in ABS or PLA. I don't have a lot of experience with PLA but I think it's at least as strong as ABS. I printed this at 50% size in green ABS. The carabiner in the picture is 5.5" and 7/8" thick. It's a good chunk of plastic but it needs to be pretty big to be strong in ABS. I hung a swing from it in my basement and it easily held my weight (uh, lets say less than 200lbs). Be careful if you try it. Don't use it for climbing or safety critical applications.
I made this with Tinkercad and openscad. Tinkercad for the body and scad for the screw threads. The body is all original, the screw threads I modified from a script by NielsJL in the Tinkercad Community. BTW his script is modified from an example in the SCAD program itself. It is the only thread design, and I mean the ONLY one that will produce a configurable nut and bolt that will print reliably in Nylon. I've tried pretty much everything out there.
The hinge on my carabiner opens sideways because support material becomes an issue if it is printed to open in the "normal" way. Print the carabiner horizontally and the nut vertically..
NielsJL bolt: https://tinkercad.com/things/9SSHITeKzx2