I am not sure about the BX1860, but the BX2660 takes a 30 mm socket. I use an impact driver to remove them, but if you don't you can use a piece of 2x4 to block and hold the blades. On the outside blades, I have also held the nut on the pulley on the top side while loosening the blade bolt. Be sure to replace the cupped washers like they came off.
I torque them to 75-80 foot pounds.