Minecraft wiki entry for Item_repair, associated text: The greatest benefit is gained when the two items have a combined durability of at most approximately 95%, in any combination, such as 47.5% + 47.5%, 94% + 1%, 10% + 10% or any other values that total 95% or less. The order in which items are combined does not matter; one sequence of repairs gives exactly the same durability as any other.