Just a thought, but wouldn't it better if you separate the tools from the base character animation itself?
For example, instead of having Pickaxe animation taking out the whole spritesheet on its own, you take the Pickaxe item out to another 4x5 spritesheet, and the character only have that mining-like hand swinging animation. This way I could reuse that animation for other thing, for example using Hoe.
Same with Sword animation. You extract the sword item on its own 4 direction animation, and the base character only have that "swinging-like" hand animation. Of which, later on, I could reuse it if I have scythe item by putting it on a new layer.
Because the motions of your hands when you are using pickaxe, hoe, axe, (or any tools that you swing it vertically) basically the same. Same with sword or scythe (or any tools that you swing it horizontally), since they should share the same slashing motion.
This will make it easier if we want to have different colors for our tools since we dont need to touch any thing but the tool spritesheet itself
Hard to explain with text, I hope you get what I mean.