You can use the Craft skill to repair an item:
Repair an Item
You can repair an item by making checks against the same DC that it took to make the item in the first place. The cost of repairing an item is one-fifth of the item’s price.
Action: Craft checks are made by the day or week (see above).
Retry? Yes, but each time you miss by 5 or more, you ruin half the raw materials and have to pay half the original raw material cost again.
What does that actually mean? There seems to be a pretty crucial piece of the puzzle missing here: namely, what actually happens based on this check?
But wait! It gets more confusing!
The broken condition itself seems to have completely different rules:
Non-magical items can be repaired […] through the Craft skill used to create it. Generally speaking, this requires a DC 20 Craft check and 1 hour of work per point of damage to be repaired. Most craftsmen charge one-tenth the item’s total cost to repair such damage (more if the item is badly damaged or ruined).
This seems reasonably clear, but it’s totally different from what the Craft skill itself says.
Moreover, the rules for sundering seem somewhat unclear on precisely what remains of an item destroyed (reduced to 0 or fewer HP, rather than merely the less-than-half that triggers the broken condition). Is that what the Repair an Item use of the Craft skill is for? Maybe, but that doesn’t actually seem to be stated anywhere. In fact, so far as I can tell, the rules seem to imply that a destroyed item simply no longer exists, has nothing left, not even dust. As one friend put it, the item has “entered the rules hole.”
I feel pretty comfortable reading and interpreting Pathfinder’s rules, but I’m seriously at a loss with this. Is anyone aware of any rules I’ve missed, or any clarification, errata, or developer explanation? For reference, I really need to know what the rules themselves actually are, or failing that, a real consensus among the Pathfinder community, because this is for a third-party product that needs to be compatible with Pathfinder. Hard to do that when I don’t even know how Pathfinder is supposed to work in this regard. As such, personal experience or preference is not useful to me, and cannot make an acceptable answer to this question, unless you can demonstrate that your approach is a widely-used one or something.
Best Answer
Both rules are correct
You can pick which method you want to work with:
If you have a longsword (hardness 10, 5 hp, price 3 gp) will gain the broken condition after 3 points of damage, and is destroyed at 5 points of damage. For our example, let's assume our longsword took 3 hp damage.
Using the Craft(Weapons) skill, we first turn that 3 gp into 30 sp to calculate the repairing progress. And we must spend at least 6 sp on raw materials. The DC to repair a martial weapon is 15, so with a +5 bonus on this check (which is not difficult to obtain), a Take-10 results on 225 sp (15 * 15) worth of "crafting" progress done in a week. Since that is way past our milestone, we can instead use a daily tracking score, or 32 sp of progress per day (225/7). In other words, this repair can be done in a day, regardless of the damage on our sword.
If we use this calculator to check the progress by day, we will see that it takes 0.9 of a day to repair it, which means that it didnt even take all 8-hours of downtime necessary to repair it, but something along 7-or-so hours.
Using the broken condition rule for repairing, we can fix 1 hp damage per hour of work, and this would cost 3 sp on materials. This is 50% of our previous method), but the DC is 20 instead of 15, much more difficult. We now need a total bonus of +10 to make this check, which will require some skills or masterworks tools and a maybe proper forge. Anyway, Each hour of work repairs 1 point of damage, so we would take one hour repairing our longsword and the broken condition is removed, and we could spend another two hours to repair the last 2 hp damage, but that's not necessary for the sword to be useable again.
If we are talking about a an item with a lot of hp, like broken breastplate (30 hp total, broken at 16 damage), it would cost 40 sp and take 8 days on method #1, while it would cost 20 sp and take at least 16 hours (2 work days) on method #2.
So, you basically have two methods of doing things, paying extra and taking longer but doing a good job, or being cheap and rushing things for a quicker fix.