For motors having a journal with one or more groove regions and a shaft
for relative rotation in the journal, aspects include providing a dual
tapered shaft. The shaft may be tapered by the application of a wear
resistant coating at least opposite the groove regions. The coating
introduces a shaft taper from near a top end and from near a bottom end
towards the shaft middle. The shaft taper may provide for improved
pumping efficiency. The coating may be applied in various processes such
as chemical vapor deposition or physical vapor deposition to establish a
thickness gradient of coating material from near the top end and near the
bottom end towards the shaft middle. In one example, the coating includes
a DLC coating. Additionally, shaft portions may be shielded to prevent
coatings thereon.