Lug nut material?

I am somewhat disgusted with the quality of the lug
nuts supplied with the Revolution wheels I was using
last year (threads not centered, material way too
soft, company now out of business, etc.).  The guys at
work (a first class aerospace machine shop) have 
hex stock that is basically scrap (material is fine,
with certs and everything).  They can duplicate the
lug nuts on an NC machine for cheap, complete with
undercuts, bearing surface, heat treat, and
engineering hard chrome.  They can also leave the ends
open.  Question is, what material to use?  everything
I can find says "steel".  A286? 4140? 321? 347? Etc.? 

Soave
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