I just wanted to make this suggestion here, since I already wrote a comment on curse, I am normally using Fun Ores or Base Metals for Extra Ores and I noticed that some of the Metals and Alloys they add are not included as Tool Parts in this mod, for example Osmium, Titanium, Aquarium, Mithril, and so on. I can try and give a full list of the metals if that would be neccessary.

Thanks for this really great mod and thanks for maybe trying to add the other Metals ^^

Edit: I had some time on my hands and played a bit with friends on our Server, I hope you don't think this is rude or anything, but I thought I'd provide a quick List of the Materials that Base Metals and Twilight Forest add, that could be interesting to include in your mod in some form. Again, sry if that seems rude, I just thought maybe it could make things easier for you, if you decide to add this stuff ^^*

Base Metals

Zinc

Hardness: 1
Durability: 1
Enchantibility: 1

Zinc is worthless on its own and is not even strong enough to forge into tools, but can be used to make the metal alloy brass by combining it with copper.

Tin

Hardness: 3
Durability: 1
Enchantibility: 2

Tin is an extremely soft metal that is not very useful by itself, but can be combined with copper to make bronze.

Copper

Hardness: 4
Durability: 4
Enchantibility: 5

Copper is soft, easy to work, and fairly abundant. It is needed to make bronze and brass metal alloys.

Silver

Hardness: 5
Durability: 4
Enchantibility: 6

Silver is a soft, shiney metal that is valued for both is beauty and its alchemical uses.

Lead

Hardness: 1
Durability: 1
Enchantibility: 1

Lead is a very soft metal that is best known for being very heavy and somewhat toxic. Lead tools are fragile, but can dish out a lot of damage when used as weapons.

Nickel

Hardness: 4
Durability: 4
Enchantibility: 7

This metal is as soft as copper, but it has alchemical properties and forms the metal alloy Invar when mixed with iron.

Mercury

Hardness: —
Durability: —
Enchantibility: —

Mercury metal is a liquid, so it cannot be used like other metals. However, it is an essential ingredient for making the fantasy metal alloy Mithril.

Metal Alloys

These metals cannot be mined. Instead, they are crafted from other metals.

Brass

Hardness: 3
Durability: 3
Enchantibility: 9

This alloy of copper and zinc (2:1 ratio) is soft, but has a beautiful golden color.

Bronze

Hardness: 8
Durability: 4
Enchantibility: 4

This alloy of copper and tin (3:1 ratio) is as hard as iron, but not quite as durable.

Steel

Hardness: 8
Durability: 15
Enchantibility: 2

This alloy of iron and carbon (8:1 ratio) is as hard as iron and much more durable.

Invar

Hardness: 9
Durability: 10
Enchantibility: 3

This alloy of iron and nickel (2:1 ratio) is slightly harder than steel, but somewhat less durable. Invar pickaxes can mine blocks that normally requires a diamond pickaxe (such as obsidian)

Electrum

Hardness: 5
Durability: 4
Enchantibility: 10

This alloy of silver and gold (1:1 ratio) can be enchanted like gold, but is a little more durable.

Fantasy Metals

These metals have magical properties and cannot be found in the Overworld. Some of these metals can be mined in other dimensions while others are alloys crafted using other fantasy metals or magical ingredients.

Cold-Iron

Hardness: 7
Durability: 7
Enchantibility: 7

Cold-Iron is a magical metal that is nearly as strong as iron. Tools made from cold-iron are extra effective against denizens of the Nether and any other creature that is immune to fire. A full suit of cold-iron armor will protect you from harm by fire and lava.

Adamantine

Hardness: 12
Durability: A lot!
Enchantibility: 0

Adamantine is a rare magical metal that is stronger than diamonds! Armor made from Adamantine make you practically invulnerable. Tools made from adamantine are extra effective against monsters that have more than 10 hearts of health.

Mithril

Hardness: 9
Durability: 9
Enchantibility: 9

Harder than steel and stronger than iron, Mithril is a magical alloy of silver, mercury, and cold-iron (2:1:1 ratio). Mithral weapons are extra effective against undead.

Aquarium

Hardness: 4
Durability: 10
Enchantibility: 15

Aquarium is a magical alloy of copper, zinc, and prismarine crystals (2:1:3 ratio). Aquarium weapons are extra effective against aquatic creatures and wearing a full suit of aquarium armor will allow you to breathe underwater and provides extra protection while submerged in water.

Star-Steel

Hardness: 10
Durability: 25
Enchantibility: 12

Star-Steel is a mysterious material that can only be found in the Ender dimension. It defies standard physics and pushes the limits of the mind. Armor made from Star Steel reduces the weight of the wearer, allowing the wearer to jump higher and fall slower. Star-Steel tools slowly repair themselves while held.

Twilight Forest

Knightmetal

Hardness: ?
Durability: ?
Enchantibility: ?

Knightmetal Ingot is an item obtained from smelting Armor Shard Clusters. Like iron, Knightmetal Ingots can be used to craft a Knightly Pick, a Knightly Axe, a Knightly Sword and Knightly Armor. Knightmetal Ingots can also be used for components of the Block and Chain weapon, using a Block of Knightmetal, some Ingots and a Knightmetal Loop in a shapeless recipe.

Fiery

Hardness: ?
Durability: ?
Enchantibility: ?

Fiery Ingot is an item crafted from Iron Ingots and Fiery Blood/Fiery Tears. Fiery Ingots contain a magical property that creates a fiery property in crafted equipment.

Ironwood

Hardness: ?
Durability: ?
Enchantibility: ?

Ironwood Ingot is an item that can be obtained from smelting Raw Ironwood Materials. Ironwood Ingots can be used similar to iron or other materials to make tools and armor. The magic of the liveroots even leaks through into the finished items, imbuing them with minor, but useful enchantments.

Steeleaf

Hardness: ?
Durability: ?
Enchantibility: ?

Steeleaf is a tool and armor material found in Labyrinth, Hollow Hill, and Dark Tower chests. This material is as powerful as Diamond in a tool or armor, but is less durable than even Iron. Like most other Twilight materials, items crafted from Steeleaf are automatically enchanted. Non-enchanted pieces can be found in Labyrinth chests as well.

I've added the base metals in an unofficial addon here: https://minecraft.curseforge.com/projects/toolbox-addons

I might add Twilight Forest if I have the time. If you have any problems with the balancing of the tools just tell me, I basically just did the best I could trying to balance them to the existing copper tool head in toolbox.