Metalworking

This is the idea the whole mod is built around, so it's worth reading before you build your first machine.

Machines don't know when to stop

A Feedback machine doesn't run a recipe. It does one physical thing, like hitting, pulling or rolling, to whatever you give it, and it keeps doing it for as long as it has power and something to work on. It has no idea what you wanted to make.

So when a Mechanical Hammer turns your copper ingot into a copper plate, it carries on hitting the plate. Leave it and the plate becomes foil. Leave it longer and the foil becomes scrap. The machine never failed. You just weren't there to take the plate out.

Getting the item out at the right moment is the game. Instruments, gearing, timers and controllers are all ways of getting better at that.

Work, strength and hardness

Three things decide what a blow does:

Strength (St): how hard one blow lands. It's printed on every machine and depends on how you've geared it. A Hand Hammer swings 1, 3 or 5 St (7 with Strength), as you choose; a Mechanical Hammer lands 3 on a long throw and 12 on a short one.
Hardness: a property of the metal. Copper is 1, iron 6, steel 15. JEI shows it on every metalworking page, and so does Materials.
Work (Fu): how much shaping the piece has taken so far. Each step (ingot → plate, plate → foil…) needs a set amount: a fixed figure plus a bit more per point of hardness. A copper plate is 14 Fu, copper foil 9 more; a steel plate is 60.

The rules:

A blow weaker than the metal's hardness does nothing at all. It's not slow, it's impossible. A hand hammer (7 St at the very most) will never shape steel (15), however long you swing.
Each blow does strength ÷ hardness in work, rounded, never less than 1. A 3 St swing on copper is 3 Fu; a 24 St blow on steel is 2.
Extra work carries over. If a blow does more than the step needs, the leftover goes straight into the next step. A hard enough blow on a soft enough metal can skip past the thing you wanted entirely.

That last rule is why strength is a choice and not just "more is better". Copper, with a 14 Fu plate and 9 Fu of foil after it:

Blow	Per blow	Plate after	Foil after
Long throw, 3 St	3 Fu	blow 5	blow 8
Short throw, 12 St	12 Fu	blow 2	blow 2: the same blow

On a short throw the blow that makes the plate carries 10 Fu over, and the 9 Fu of foil is already done: you never see a plate. On a long throw you get a plate on the fifth blow and three blows to grab it.

Watching progress

You don't need an instrument to avoid ruining things. Look at the workpiece with Jade, or hover over it, and it tells you how far along it is: Barely marked, Taking shape, Visibly worked, Nearly there.

Carry Calipers and that turns into an exact figure, like "9 / 14 Fu". That's what you want when you're aiming for something that only lasts a blow or two, like foil.

Hot metal

Some metals, steel for one, can only be worked inside a temperature window: steel's is 900–1100 Tu. Too cold and the blow does nothing; too hot and it does nothing either. The metal is never damaged by a blow at the wrong heat, you just have to reheat it.

Hot items cool down wherever they are, at 30 Tu a second: in your hand, in a chest, in a hopper. Steel at the top of its window has about 7 seconds of working before it's too cold. See Heat. The trip from the fire to the hammer is a race, and a hot piece burns bare hands: see Hazards.

Wear: hitting the wrong thing

When a blow can't go into the metal, it goes into the machine instead. That happens when:

the metal is too hard for the blow,
the metal is the wrong temperature,
the blow is harder than the machine is built to take (over-geared), or
there's nothing left to make (scrap stays scrap).

The machine slowly wears from this: Head is marked (below 98% condition), battered (below 85%), spent (below 65%). A worn machine hits softer and can take less. It bottoms out at 50% and never breaks completely or stops working. About 600 wasted short-throw blows (ten minutes on a water wheel) takes a hammer from new to its floor.

Running a machine correctly never wears it, however long it runs. A hammer pounding empty air doesn't wear either. If one of your machines is worn, something specific went wrong, so go and find it. Calipers can measure exactly how worn a machine is (switch it off first).

The other shaping machines

The hammer is one of several. Each does a different action, and each makes a different chain of products:

Machine	Action	Chain
Hand Hammer, Mechanical Hammer, Mechanical Press	hammering	ingot → plate → foil → scrap; nugget → bullet
Wire Drawer	drawing	rod → wire → fine wire; plate → case
Rolling Mill	rolling	ingot → rod
Drill Press	drilling	plate → drilled plate → swarf; gun parts
Lathe	turning	rod → turned rod → swarf; grips; gun parts
Grinding Wheel	grinding	ingot → ground ingot → swarf; gun parts

The drill, lathe and grinder cut rather than hit: the tool has to be harder than the metal (drill 18, lathe 20, grinding wheel 30), and then each cut removes strength ÷ hardness in work. They also make and shape gun parts.

Progress doesn't carry from one action to another. A half-hammered ingot put in a rolling mill starts from zero.

JEI lists every step for every metal, with how much work it takes and how hard the metal is.