I was doing some bike maintenance today and wanted to disassemble my rear hub. It turned out that I needed a 12mm Allen bit for that, which I don’t have. So I 3D printed one! And it worked! Torques safely to 5Nm and I only needed 4Nm for the job. Haven’t tested higher torques.
I don’t think the tolerances would be too bad. A lot of prints that have tight tolerances have a test piece that you print and test against a known object, which let’s you adjust your print to get tighter tolerances. Once you correct for the expansion of the plastic, getting the right tolerances should be totally doable.