Chas- thanks for your help! Indeed, it is a 6mmx1.00 screw. The one I got from the hardware store was in the wrong bin-NAPA dude set me straight today. Tested new screw in other side and worked perfectly. So...
my locknut threads have been stretched (which is prolly why the bolt snapped). I'm 3 for 3 with the die this year which means: either I'm good at this or my luck is about to run out.
