Don Teach mention punches for making gaskets.  I have been using Boehm
Hollow Punches for a long time.  They are interchangeable to make any
configuration of I.D. and O.D. together in one punch.  I bought my set
from Garrett-Wade back in the 1980s but they don't carry them any more.
Here's a few sets:

http://www.amazon.com/Mayhew-66002-8-Inch-2-Inch-Imperial/dp/B000X35UQ8 
http://www.amazon.com/Anytime-Tools-HOLLOW-LEATHER-GASKET/dp/B000Q7AVL0/ref=pd_sim_sbs_hi_1 
http://www.axminster.co.uk/boehm-boehm-hollow-punch-sets-prod22429/ 

Regards,
Jon Page