3x3x3 Hammer Help

I have been trying to make a 3x3x3 hammer (as in a cube with three block dimensions) and it has been failing miserably. I have found a few posts about 3x3x3 hammers/pickaxes but none have direct tutorials or have errors. I have currently tried to make one by modifying the xisting hammer preset but it does not break poroperly. If anyone knows how to make a 3x3x3 hammer, please help.