Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:4138286.

Fittings I made for a T, Coupling and Flange for 3/4" structural steel pipe (or SteelTek pipe from Lowes). All printed in ABS with a 0.6mm nozzle at 0.4mm layer height. All parts tested to work and used to build a mini desk for a keyboard/mouse.

All fittings have holes for 1/4-20 screws, which I drilled at tapped using short 5/8" screws to hold the pipe securely in place. The T fitting requires two parts Inside and Outside as well as 2x 2.5" long 1/4-20 screws and 2x 1/4-20 nuts. Alternatively you could probably drill and tap for M6 screws.