42" Riding Mower two blade replacement - is there a proper alignment?

[Rover_Hokie]

I have replaced the two-blade system of riding mower blades before, but maybe I am just OCD now in my old age. I searched and watched some videos on YouTube, and searched the forum, but there seems to be no real rhyme or reason as to how the blades are positioned in relation to each other as they go around when the blades are installed. Example: When re-installing blades should one be installed at the 12 o'clock to 6 o'clock position while the other is installed 90 degrees to it pointing from 9 o'clock to 3 o'clock, or does it matter at all when the blades are rotating when mowing?

 

[Rivets]

This will depend on whether you have a timed or untimed set up. If you have an untimed system, blades don't touch even when you have them installed end to end, it does not matter. If you have a timed system, blades will touch, one blade should be installed at a 3--9 position and the other at a 12--6 position. With this setup you will also have a cogged belt coupled with a cogged pulley.