I have found the best solution for having dull Arch Punches sharpened:
Joyce Brite.  I sent her several of my terribly dull punches and she
sharpened them.  She did a fantastic job - they are incredibly sharp
now!!  So sharp, that I didn't realize how dull they really were.  I
recommend that anyone who needs arch punches sharpened contact Joyce.
Her e-mail address is: brite@ksu.edu

Cheers,

S. K. Goodman