cross shaft question

Got another question for you, currently i am making a set of control arms for a nissan hardbody, right now i have ordered the end links with poly bushings, heres my problem, nissans use a cross shaft for there control arms, the sleeves that come with my poly bushings need have a 9/16" hole, the shafts have a taper that starts at 11/16 and goes down to around a 1/2" or so, the question is would it be safe to machine down the shafts to 9/16" so i can run poly bushings, if its unsafe its no big deal, i can always use the stock rubber bushings, thanks for the time.

You can machine the shaft down with no issues, but be sure to use a radiused cutter so that you don't create any stress-risers.

Can you explain what tool that would be to use please? 

He just means to use a cutter that cuts a round edge instead of going straight from the larger to smaller sizes.  If there is a straight edge between the 2 sizes, it will break there.

Just make sure that when you put the cross shaft in the lathe and turn it down to 9/16" that when you come to the thicker part of the shaft that there is not a sharp corner there.  Grind a cutter with a small radius on the tip or use an insert (if your using a quick change or similar tool holder) with a small radius in it.  This will leave a small radius in the corner and will not break as easily as a sharp corner.

AHHHH ok, the help is greatly appreciated guys!