"You paid for 1,000 tons. You received 970 tons. Where did the money go?"
In the steel business, weight is money. But surprisingly, "Weight" has two definitions.
If you buy on Theoretical Weight but sell on Actual Weight, you are guaranteed to lose 3-5% of your capital instantly.
Today, we expose the "Negative Tolerance" trap and how to stop paying for air.
1. The Two Weights: A Dangerous Difference
Why is there a difference? Because steel is not always rolled perfectly flat.
| Type | Definition & Risk |
| Theoretical Weight (Calculated) |
Calculated by math: $$Weight = Volume \times Density (7.85)$$ The Risk: It assumes the steel is perfectly thick (e.g., exactly 10.00mm). In reality, mills roll it slightly thinner (9.7mm) to save metal. |
| Actual Weight (Scale) |
Measured by a Weighbridge or Draft Survey. The Reality: This is the physical steel you actually get. It is usually lighter than the theoretical weight. |
2. The "Rolling Tolerance" Loophole
Steel standards (ASTM, JIS, EN) allow a Thickness Tolerance.
For a 10mm plate, the tolerance might be $\pm 0.3mm$.
📉 How Mills Make Money
- The Goal: The mill intentionally targets the Negative Tolerance (e.g., rolling at 9.75mm instead of 10.00mm).
- The Result: The plate is within standard (Legal), but it is 2.5% lighter.
- The Billing: If the contract says "Invoicing on Theoretical Weight," the mill charges you for 10.00mm (100% weight) but delivers 9.75mm (97.5% weight).
- The Loss: You essentially paid for 2.5% "Air."
3. Draft Survey vs. Weighbridge
When you receive the cargo, how do you prove the shortage?
- Draft Survey (Ship): Measures how much water the ship displaces. Accuracy: $\pm 0.5\%$. Good for bulk cargoes (20,000 tons+), but not precise enough for small claims.
- Weighbridge (Truck): Weighs each truck. Accuracy: $\pm 0.1\%$. This is the most accurate method.
- Conflict: Mills often refuse Weighbridge reports, claiming "Scales differ." You need an independent surveyor (SGS/Intertek) to witness the weighing.
4. Strategic Defense: The "Weight Clause"
To avoid this trap, you must negotiate the Weight Clause in your contract BEFORE signing.
- Best for Buyer: "Invoicing based on ACTUAL NET WEIGHT as per Mill's scale." (You pay for what you get).
- Compromise: "Theoretical Weight, but limited to +/- 0.5% difference from Actual."
- Worst for Buyer: "Theoretical Weight Final." (You accept the rolling tolerance loss).
Expert Verdict: Check the Density
Also, check the Density factor. Carbon steel is 7.85. Stainless steel (304) is 7.93.
If you use 7.85 for Stainless Steel, you are calculating it wrong.
Don't let the math eat your profit.
Next: Negotiation Strategy
👉 [Negotiation] The "Walk Away" Point: Calculating BATNA⚖️ Disclaimer & Privacy Notice:
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