I've been waiting on an order of t-nuts for some 8020-1010 aluminium extrusions that I have (note: the imperial version). Rather than wait further, I designed my own to work with the M5 bolts that I have.
The design has been tested and works beautifully; the M5 should thread into the ID of the nut and hold firm.
let me know if it needs any tweaks.
T-Nut.stl | 751.6KB |