It might be helpful if you let us know what style of hammer you might be thinking of. There are spring arm hammers similar to the Little Giant, helve hammers, strap hammers, compressor hammers, motorized treadle hammers, etc. Other information may be helpful as well such as the weight of the hammer action, what your end use will be (knife making, steel decorative work, etc.) Many styles of hammers could be built but there are a lot of variables. Help us out here.