Upgrading Tools

I found that there are alot of mods that just kind of take away from the game. Making diamonds from dirt, and what not. I couldn't find a mod that would let me do this, so I made one myself. At the moment, it only works for pickaxes. Trying to figure out why it doesn't work for other tools.

But in case the pictures don't explain this mod well enough, here's my sales pitch:

Have you ever been mining in caves when you realize you forgot your sticks?
Yes!

Have some extra iron ore in your inventory?
No, I already smelted it into ingots :/

That's perfect! You can upgrade your junky stone pickaxe, with this mod, Tool Upgrading!
Really? Can it work with other types of pickaxes too?

Yes! You can upgrade a wooden pickaxe to stone, iron or diamond, stone pickaxes can upgrade to iron or diamond, and iron can upgrade to diamond!
Wow really? How does it work?

That's simple! just make the pickaxe like you normally would, but instead of sticks, put the pickaxe you wish to upgrade in the center!
Wow, really? That mean's I'll never run out of my precious sticks I use for torches! But does it work for other tools as well?

Not at the moment, but our engineer is developing a similar method for the other tools!
So how much does it cost?

For the value of Four stacks of sticks, you can have it free! That's right, Never use sticks for pickaxes again!
That's amazing!

(pictures soon)