You can reverse a universal motor by reversing ONLY the armature (brush wires, typically) OR only the stator. Reversing both doe nothing, it already runs on AC, after all.
So the switch has to reverse the brush wires relative to the stator wires, which means generally brush wires are connected to the center terminals of the switch you illustrated. Wires from the right side pair of terminals go to where the brush wires normally would go to.
Might be good to shut off before reversing.... otherwise it is a direct reverse at speed. That is both rough on the motor and it also draws a lot of current.
1601
Keep eye on ball.
Hashim Khan