rhmorrison is good at this. usually we use the unstandard coupling like this. make a sleeve for a big size coupling ourselves. but the coupling and shaft gap can not too big. you can get the 8mm shaft coupling here: 8mm coupling -leso VDX Wrote: ------------------------------------------------------- > ... i used pneumatic tubes for coupling 5mm shafts > to M5 threaded rod ( > >by lusocal - Mechanics