For the past two years when I shoot my broadheads I always use NEW arrows. Anyhow I have to turn my arrows to a different odd feather(sometimes) to get them to be dead center. It is not a big deal I like that I can do it, but what causes this?? Differnet spine? Like I said it aint nothing for me to drill the center out with every arrow once I turn the arrow just curious??

Great question. I've ran into the same thing. Turning the knock and the arrow flys great...

Spine inconsistancy. By turning the nock you are adjusting your arrows so that the stiffest part of the spine is at the same place on all arrows with relation to the string. That way all of the arrows should shoot the same. There are a number of threads that discuss this. here is one: http://www.huntingnet.com/forum/tm.aspx?m=2274552

Thx Bruce so if im thinking right, this is where an arrow spinner would come in handy when fletching the arrows? Find the stiffest part of the arrow and put odd feather there? I think this would work?!?!

If you ever hear of "floating" an arrow, this is what they mean. Float your shafts in water and the heavy side will be down. Mark them all on the top side and index your nocks with your mark

Depends on how you shoot, odd up, out or down, you want the heaviest side of the shaft down.

I I'd guess that it's most important to have them all the same.

An arrow spinner is just for determining the straightness of the shaft, it won't show you the stiffest side.

From what I have read from more experienced people, yes, you put the cock feather there but I am thinking that is if you shoot cock feather out(to the left for a RH shooter). I believe the reason for that is that is where the most force goes to the arrow on the shot(perhaps just for finger shooters though). Perhaps someone else will chime in on that.

What Kodiak says seems to meis what matters most. Have them all the same and then tune your bow and arrows together.