Item Repair
Item Repair is a feature added in Beta 1.9 Pre-release 3 (or 1.0.0 not including development builds) which allows players to repair damaged Tools, Armor, or other items with durability by combining them on a Crafting grid.[1][2] Two items of the same type and material can be placed anywhere on the crafting grid, and the result is a single repaired item. The repaired item will have usage points equal to the sum of the old items' usage points plus a 'repair bonus' of 10% of the item's maximum uses, up to a limit of the maximum durability for that item.
Even if both items were enchanted with the exact same enchantments, the repaired object will always be unenchanted. The player can always re-enchant it again later. Hence, given the current (as of version 1.2.5) random enchantment system, using a 'junk' item in a repair may sometimes be useful for removing an unwanted enchantment from an item prior to trying to enchant it again.
Repairing gives a slight benefit in conserving inventory space, as it combines two non-stackable objects into one[3], and the ~10% 'repair bonus' allows you to get slightly more total uses out of tools, which helps eke out resources a little further.
Tools made of different materials (for example, a wood and a stone pickaxe) cannot be combined.
[edit] Formula for Uses Restored
The formula for determining how many uses a repaired item will have restored to it is as follows:
min( floor( Item A uses + Item B uses + (Max uses / 10) ), Max uses)
('floor' means round down to the nearest integer, 'min(a,b)' means whichever of a or b is smallest.)
Example: Two stone axes have 10 and 45 uses. A newly-crafted stone axe would have 132 uses.
- 10 + 45 + 132/10 = 55 + 13.2 = 68
This algorithm gives the greatest benefit when both items combined have 90% or less of the maximum uses of one item remaining, allowing the full 10% bonus to be added. You can combine 45% + 45%, 89% + 1%, or 1% + 1% for maximum efficiency, as long as the sum stays under 90%. The order in which items are combined does not matter. One sequence of repairs results in exactly the same durability as any other.
A good strategy is to wear down one item until it's definitely under 45%, but not so damaged that you might accidentally break it. Do likewise with another. Then put both in your crafting slots, and see if the result has a damage bar. If it does, you can repair right away. If it has no damage like a new item, there is most likely an excess that you would throw away, so it's more efficient to defer repair.
