The pins break because the 23mm hex is being bottomed out against the pin. You need to shim the axle to the point where that small lip around the center of the rear of the hex is against the outermost shim, don't tighten the hex down against the pin. You don't need any hardened pins if you set the assembly up correctly, and don't overtighten those axle nuts. I posted at MV bashers about braking pins, eating bearings, and losing 23mm hex nuts if you care to read it.
http://mvbashers.proboards21.com/ind...ead=1117293871