This is a Yaw Hinge for a Mantis Stereo Microscope (original P/N 187-C-0107). This piece commonly breaks, and parts are no longer available for the original Mantis from Vision Engineering. When I purchased my Mantis, this piece was broken and had been epoxied back together... then that broke one day while using it, so I epoxied it again. That failed a couple months later. So, I decided to design and print my own replacement part.
I designed it in two pieces, since the top doesn't really add any strength, and would be a waste of time/support material to print as one piece. The top just snaps into place, and when the bolts are in, the top is captured so it can't come out. I also attempted to strengthen common failure points.
Unless you have a good temperature controlled chamber, I'd recommend printing this in PLA. I printed mine in (natural) ABS on a Creator X (clone) with a plexi window and hood... the chamber stays around 50C with no drafts, but I still had some warping, which caused a couple of the layers to seperate. This caused my first one to fail. I made a couple changes to the model for more strength, but still had a couple of minor seperations on the second print... so I used an old soldering iron tip to re-melt those layers and make sure there was a good bond (you can see the discoloration in a couple parts in the pics). I'd guess that a PLA version wouldn't have warped at seperated like that.
Attached are the STL files, as well as the Sketchup design file. My printer made the holes and hex nut/bolt grooves slightly smaller than they should have been, so I expanded them just a bit in the model. This shouldn't cause any problems since they don't need to be perfectly sized (but if yours prints too small, this will save you time from having to file out the holes).
BTW, I see someone is selling a 3D printed yaw hinge on ebay... that's not me, not my model, and (IMO) is pretty outrageously priced (or maybe I'm just cheap).
Print the main hinge and top parts (see my note in the description regarding ABS vs. PLA).
-I didn't care about looks/detail, so I printed it with a 0.3mm layer height.
-I bumped up the number of shells to 4 for added strength
-I used 30% infill (30% is plenty strong... layer bonding is really the only worry with this part)
Once printed, snap the top into the main piece, being careful not to bend the sides outward too much.
Insert bolts and nuts, re-attach the spring, tighten, replace the caps, and get back to work!