Technical · Billet Geometry
Steel Billet Size and Tolerance Guide
Grade chemistry and billet geometry are separate agreements. A size and tolerance schedule states what the mill will accept at the furnace, and every limit in it needs a measuring basis attached — a tolerance without one cannot be verified.
No numerical tolerance table is reproduced on this page. Limits remain order-specific and subject to written confirmation.
Every schedule needs
- The nominal dimension and its permitted variation.
- The measuring basis each limit is judged on.
- The condition the material is measured in.
- Whether every piece or a sample is checked.
- The disposition route for a piece outside the limit.
Size schedule
Agree the geometry as its own schedule
Each row names the decision, the applicability limit that applies, the evidence to obtain and the action that closes it before the order is released.
| Decision | Applicability and limit | Evidence to obtain | Closing action |
|---|---|---|---|
| Cross-section | Nominal size alone does not state the permitted variation. | Nominal dimension and its tolerance, with the measuring basis. | State millimetres and the direction of measurement. |
| Length | Cut length drives furnace charging and yield. | Nominal length, cut tolerance and the measuring convention. | Agree whether length is measured cold or as-cut. |
| Shape | Squareness, corner radii and twist affect the first pass. | Shape limits and the inspection method that verifies them. | Record the shape criteria, not only the outside dimension. |
| Straightness | Deviation is measured over a stated length, not in total. | The permitted deviation and the reference length. | Fix both figures before the order is placed. |
Measuring basis
A limit you cannot verify is not a limit
Four things turn a stated tolerance into something the receiving mill can actually check.
Measuring basis
A tolerance value is meaningless without the basis it is measured on.
State the instrument, the reference and the measurement conditions.
Sample or full check
Whether every piece or a sample is measured changes the acceptance.
Agree the sampling frequency and who performs it.
Condition at measurement
Hot or cold, as-cut or conditioned, the measured value moves.
Fix the condition the limits apply to.
Disposition of a deviation
What happens to a piece outside the limit must be decided beforehand.
Agree the concession route and who authorises it.