Specification
How to specify a clad disc for your factory
A specification is the only document that survives a batch dispute. This guide lists the fields worth writing down, the ones that only look necessary, and the order to decide them in.
At a glance
Specification at a glance
| Field | Why it is specified | Typical mistake |
|---|---|---|
| Layer grades | Decides corrosion, induction, cost | Leaving the hob face grade unstated |
| Per-layer thickness | Decides heat spread and draw | Specifying only the total |
| Diameter and tolerance | Decides yield and fit | Tolerance tighter than the press needs |
| Flatness | Decides seating in the die | No measurement method stated |
| Surface | Decides appearance and tooling | Pattern left to the supplier |
| Documents | Decides acceptance at the customer | Requested after production |
Start with the cookware, then the fields
The specification is derived, not invented. Start with the pan: diameter, draw depth, wall thickness, target weight, hob type and the finish the customer expects. Those six decide the rest.
A thick wok with a deep draw needs a different total thickness from a shallow milk pot, even if both use 304 + 1050 + 430. Writing the grade first and the thickness second is how buyers end up with material that is correct on paper and wrong in the press.
The fields that must be written
- Grade of each layer, in order from the cooking face outwards.
- Thickness of each layer, and total thickness with tolerance.
- Form: disc, single-ear blank, double-ear blank, square blank or sheet.
- Diameter or width and length, with tolerance.
- Flatness, with the measurement method and reference surface.
- Surface per face: plain, embossed or etched, and the pattern.
- Edge condition.
- Documents: certificate, ROHS, REACH, food-contact report, inspection record.
- Packing and marking.
The fields that are usually noise
Buyers often specify a hardness or temper they cannot use, or a surface roughness figure that the pan maker will remove at polishing anyway. Both raise the price without improving the part. The test is simple: if the pan's acceptance test does not measure it, question whether the specification needs it.
The other common noise is an over-tight diameter tolerance. A disc cut to plus or minus a fraction of a millimetre that the press does not need adds cost to every disc in the order.
Order of decisions
Decide the structure, then the total thickness, then the diameter, then the surface, then the documents. Each decision constrains the next, and doing them in that order means the supplier can answer each one with a real number instead of a range.
Once the specification is written, the sample is checked against it and the bulk order references it. That is the whole discipline, and it is what makes a second order identical to the first.
Questions
Common questions
Do I need to specify per-layer thickness?
Yes, at least the core thickness. Two discs with the same total thickness but a different core ratio heat and form differently.
How is flatness measured?
With a stated method and reference surface, for example on a surface plate. A flatness figure without those two is not comparable between suppliers.
Should the drawing include the pattern?
Yes, for embossed or etched products. Pattern area, depth and rim width are part of the tooling or mask.
What tolerance is normal on a disc diameter?
It depends on the press and the trimming allowance. State what the press needs and the quotation confirms what the plant can hold.
Can the supplier write the specification for me?
A good supplier will propose one from your drawing and flag the open fields. The approval still has to come from your side.