This is a derivative of Sublime's Three jaw keyless chuck - http://www.thingiverse.com/thing:9179 , these are replacement jaws. From the discussion on that page hexitex may have some better jaws on the way, hopefully this principle can be applied to them too.I angled the base of the jaws a bit (1 or 2.5 degrees) such that when they are tightened, they will want to lean in towards whatever they are holding a tiny bit, applying more clamping force.Note that there are four files, two each for 1 and 2.5 degrees. The difference in each pair is the orientation of the lean. The "reverse" files are in case you want to turn the jaw backwards to grip larger objects (so it will need to lean the other way)