Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:4962860.
I saw this chain connector on a YouTube video and thought it would be a cool item to model and print out. I have included 3 different center pin sizes to accommodate different printer tolerances. Print them out at whatever settings you want for the strength you are looking for. It is kind of small (roughly 65mm x 40mm) It should scale pretty good. The center pin is friction held. I used the largest of the three pins in my print. It holds in tight but can still be removed and holds pressure on the parts to keep them securely locked together.
Let me know what you think and if you have any suggestions.
Update Added a second version that has a pin you twist to lock it in to place.