An adjustable joint that inserts into the ends of PVC pipe and lets you set the angle between two pipes in 22.5° steps. It has 9 positions across 180°, running from a right angle on one side, through straight, to a right angle on the other. It won't bend tighter than 90° either way. Designed for the legs of a large spider prop, it works for any PVC-frame project: props, costumes, displays, frames, and supports.

Works as a reducer. The hinge interface is a fixed size, so pieces made for different pipe diameters connect to each other. You can join, say, 2" pipe to 1" pipe through the same joint.

How it goes together. Two hinge pieces are joined by a single machine screw and nut. The screw hole is a parameter (p_screw_diameter), and the STLs are set to 3 mm, which should work with M3 or #8-32 screws. Hinge thickness scales with the pipe size, so screw length is determined by the sizes of the two pieces you are joining. I also put a pan-head screw in the side, through the PVC into the insert to hold each insert in place.

STLs included for 1", 1.5", and 2" PVC.

Parametric Fusion file (.f3d) included. Key parameters:

• Insert diameter (i_pvc_id): Fits your pipe's inside diameter. 
• Connector gap (p_connector_gap): Clearance between the insert and the joint. A 3 mm gap works nicely for smaller sizes, but with 2” PVC or above, you’ll need more of a gap if you want to reach a right angle.
• Bottom flat (i_bottom_cut): Flattens the underside so it prints without supports. This also affects screw length.
• Screw hole diameter (p_screw_diameter): Adjust for a different diameter screw.
• Others: There are many other parameters and they all have comments. For instance, you could reduce the number of grooves and make them deeper for a stronger, but less adjustable hinge.

I printed with PLA, a 20% gyroid infill, and 4 wall loops, which is working fine for supporting the weight of the PVC spider legs. You could make them a lot stronger with a different filament or other settings.