6mm is way too small for a brake rod..
I used to use 3/8 or 5/16 male rod ends, then thread tubing, to put it together, think it was 1/4 heavy wall tubing.
It is nice to be able to TURN the brake plate 90 degrees OUT OF THE WAY, when removing wheel.. just leave locknits loose.
Rod ends are available at many bearing supliers, make sure you get good ones... for the rod or tube.. find a friendly machinist to do it for you..