If you find yourself needing to make small discs a lot, you may want to invest in a punch-and-die set. They're not cheap, but if you buy approximately two kits less, you can easily afford one. As a further tip, if you also want to make domed rivets, buy a regular punch-and-die set plus separate (replacement) domed punches for use in the die from the first one, which will be much cheaper than getting a second complete set of domed punches and the associated die.