Costing

How much does CNC machining cost in China?

Quotes that differ by 3× for the same drawing usually mean the factories read the drawing differently, not that one is cheating you. Here is where the money actually goes.

Two quotes for the same drawing can differ by a factor of three. In almost every case that gap is not one factory cheating you and another being honest — it is two factories reading the same drawing differently.

Here is where the money actually goes, so you can tell which quote is plausible.

The five cost components

A machined part price is built from material, setup, machine time, finishing and tooling. Understanding the rough share of each tells you where to negotiate and where negotiating is pointless.

Component	Typical share	What drives it
Material	20–35%	Alloy, raw stock size vs finished size, whether the factory stocks the grade
Setup / programming	10–30% at low volume, near zero at high volume	Number of operations, fixturing complexity, whether a new programme is needed
Machine time	25–40%	Cycle time, machine hourly rate, tolerance level, number of setups
Finishing	5–20%	Anodising, plating, bead blasting, passivation, and whether it is in-house
Tooling	0–15%	Custom fixtures, form tools, first-article inspection cost

Notice that setup is nearly free at high volume and dominant at low volume. This is why a 10-piece order and a 10,000-piece order of the same part are not on the same price curve, and why asking a factory to quote both is the fastest way to understand their real cost structure.

Why tolerance, not size, sets the price

Buyers often assume a bigger part costs more. Often it does not. A small part held to ±0.01 mm with a tight surface finish requires slower feeds, more inspection passes and possibly a second operation on a different machine. A part ten times the size at ±0.1 mm may run on a single setup at high speed.

The practical rule: every tolerance step you tighten costs roughly 15–30% more machine time. Specify tight tolerance only on the features that need it, and mark everything else as general tolerance.

Material cost: the raw stock trap

Factories buy aluminium extrusion and bar stock in standard sizes. If your part requires a stock size the factory does not carry, you pay for the whole bar or plate even if you only need a fraction of it.

• 6061-T6 aluminium bar: widely stocked, cheapest route
• 7075-T651 plate: commonly stocked in standard thicknesses, but more expensive per kg
• 316L stainless bar: often a special order, adds lead time
• Titanium Ti-6Al-4V: usually a special order with a mill certificate requirement

A good factory will tell you the stock size they are cutting from. If they cannot answer, they are guessing, and the guess will show up as a change order later.

Volume breaks: where they actually happen

Price rarely falls smoothly with quantity. It drops in steps, at the points where the factory changes production method:

Quantity	Production approach	Price behaviour
1–10	Prototype, manual setup, single operator	Highest per unit; setup dominates
10–100	Small batch, soft jaws, minimal fixturing	Setup cost spread; modest drop
100–1,000	Dedicated fixture, optimised programme	Clear step down
1,000–10,000	Bar feeder or pallet changer	Large step down
10,000+	Dedicated cell, possibly casting or forging instead of machining	Approaches material + finishing cost

That last row is worth knowing: past a certain volume, the cheapest way to make a machined part is often to stop machining it and cast or forge it near-net shape. A factory with only machining capacity will not volunteer this. A sourcing agent working for you should.

What an agent commission actually is

A transparent sourcing agent charges a percentage of the factory invoice — commonly 5–10% depending on order value and complexity. That is not a markup on the unit price; it is a fee you can see, calculated on a factory quote you can also see.

Compare that with the alternative: a trading company that gives you one blended number and earns an undisclosed margin. You cannot audit it, and you cannot tell whether the factory received a low price and the trader kept the difference.

How to sanity-check a quote

1. Ask for the material grade and stock size. If neither appears on the quote, it is incomplete.
2. Ask for the operation count. Three setups for a simple bracket is a red flag for poor process design.
3. Ask whether finishing is in-house or subcontracted. Subcontracted anodising adds 5–10 days and a margin.
4. Compare cycle time against the machine hourly rate. A credible quote can usually be broken down roughly this way if you ask.

None of this requires you to be a machinist. It requires asking four questions a good factory answers without hesitation and a bad one deflects.