I intend to use these to clamp accessories to my Taig mill, but this can be used to print t-nuts of any size. In the photo, I show t-nuts sized for a Taig mill, and also a much larger Bridgeport. The scad file uses aubenc's threading library (http:www.thingiverse.com/thing:8796). The default sizes are for a Taig t-slot, and all dimensions are in units of inches (sorry rest of the world...). Nevertheless, with some unit conversion on your part, metric threads shouldn't be a problem. Note well: these are NOT intended for machining! Plastic is much weaker than steel, and it doesn't take a lot of clamping force to shatter the t-nut. Use these for lighter applications like holding down measurement fixtures or chip-guards.I printed these t-nuts on a Makerbot Replicator 2 using medium (0.2mm) resolution, and the threads work well without any cleanup.