Summary

I designed these corners to mount some lasercut pieces inside an enclosure.

Instructions

These were made to accept 4-40 screws (.112").
The countersunk hole is for nut/lockwasher combo (McMaster #90675A005), which is why I made it circular, to account for the lockwasher, which bites the ABS.

If you want to use larger machine screws, try scaling up.

There are cylindrical holes in two axis, which I designed for aligning the pieces and glueing them to a surface. I suppose the height could be doubled for an additional set of these tunnels to connect all sides to make a rectangular frame or you could print up a second copy and bolt 'em together if you're feelin lazy.

I've already radically changed the design to suit my purposes, so I'll have to revisit this once I've finished the active project.

Modular Frame Corner