Assistant in Finding U.S manufactures for Gear Shaft

Almost any machine shop with a lathe and a milling machine should be able to do this as long as the specification is provided. I am sure almost every city with a half decent population will have at least one. The only restriction would be for extremely large shafts. If the accuracy requires 1/10,0000th of an inch, a grinding machine is required for a lathe.

Since you mentioned Michigan, here is a partial list:

http://www.mfgquote.com/profiles/CNC-Machining-Michigan.html

This guy can make it for you: ZoL inc.

Will this be a green turn or hard turn? Makes a huge difference in how you approach the machining. What is the material? Also a huge impact on the process! Finally, whats the volume? This may be the most important question!