This is a T nut for inserting into an aluminum frame 3030 extrusion like the Prusa MK3. Print them without supports, with 100% infill, and lightly sand them. Insert an M3 hex nut and push it firmly in. PETG is recommended for strength.
To use them you will need to unscrew the end of the frame, but they work well and don't wobble around. Once in the frame, they are easier to adjust and slide compared to drop in inserts.
Here are tips to design strong parts to connect to these nuts with M3 12mm screws, which work perfectly:
- Use a part that is at least 10mm wide
- Use a part that is exactly 5.2 mm thick
- Create a circle with a diameter of 3.5mm for the M3 shaft
- Create a screw head width of 6mm and indent it 1.5 mm
I use these measurements in some of my designs:
Side LCD mount: https://www.thingiverse.com/thing:3483560
Ribbon Cable Clip: https://www.thingiverse.com/thing:3485143