If you've ever changed seed tube guards that are attached with roll pins to the bottom of a planter row unit shank, you know they're a pain to remove and install. If you use a hammer and punch, the shank acts as a spring and absorbs the energy of your hammer blows. The solution is to use an air hammer. An air hammer's multiple-blows-per-second overcomes the springiness of the shank and makes removing those roll pins a breeze. All it takes is a set of roll pin punches designed to fit in an air hammer.
If you DON'T have an air hammer, this is a time when it would pay to invest in one--along with a set of roll pin punches to fit in the air hammer. A single squeeze of the trigger--Brrr-RRPP!--is all it takes to remove even the most stubborn roll pin.
Also--if you've got an older planter where the roll pin holes in the shank are "hogged out" and are having trouble getting new roll pins to stay in place, oversize roll pins are available. You have to drill out the ovaled-hole to make it round again, but then you can (air) hammer in the oversize pins and have a snug fit.