---
id: KB-IU-017
url: https://app.codecontract.io/help/manufacturing/the-machine-shop-working-to-order
idioma: en
categoria: sector-industria
subcategoria: metalurgia
audiencia: usuario
nivel: avanzado
actualizado: 2026-08-13
tambienEn: [es]
relacionados: [KB-IU-007, KB-NO-024]
citadoPor: [KB-IU-018, KB-IU-028]
---

# The machine shop working to order

_The material is either the client's or yours to buy, and that difference decides what you answer for when the part fails._

**Responde a:** machine shop part documentation · material certificate the client asks for · machined part traceability · who is liable when a machined part fails

You receive a drawing, machine it and deliver. When a part fails months later, the question arrives in two very different versions depending on who bought the material — and almost no shop has that distinction written into the quotation.

## The two situations, and what you answer for in each

| Who supplies the material | What you answer for | What you must keep |
| --- | --- | --- |
| **The client supplies it** | The process and the dimensions | Which heat it was, even though you did not buy it |
| **You buy it** | The process AND the material | The mill certificate, tied to the parts despatched |
| You buy it to their specification | The same, plus having met it | The specification, versioned |

> [!IMPORTANT]
> **A material certificate is only useful if it can be tied to the actual parts despatched.** A file full of mill certificates nobody can relate to a delivery note is paper: when the client asks about the part that failed, you will have twenty certificates and no way to say which was theirs. What ties them together is recording on the works order which material was cut, and that happens on the shop floor, not in the office.

## What to record per works order

1. **Which heat or material lot it came from** — Even if the client brought the material. Especially then.
2. **What was machined, on which machine and by whom** — It is what lets you explain a pattern if one repeats.
3. **The dimensional checks you carried out** — With which instrument, and when it was last calibrated.
4. **And which parts went out in each delivery** — Without it you cannot bound anything forwards.

> [!WARNING]
> Two things always slip through and appear in no record: **rework and the spare part**. A part touched up outside the normal flow and re-entering, or the three extra units made «just in case» and left on a shelf until someone uses them six months later. Both break the link between what was delivered and what was recorded — and the second is especially treacherous, because that part enters a future order carrying someone else's traceability.

> [!NOTE]
> What material and process documentation must be issued and kept depends on the sector you supply and on what was agreed with the client; in sectors with part-level traceability the requirements are far heavier. **Your client and your adviser settle that before you accept the order**; here we explain the split that avoids discovering it with a broken part already on the table.

**If the client brings the material, am I liable for it?**

Not for the material, but yes for knowing which it was. Record it anyway.

**Do I have to keep mill certificates?**

If you buy, yes — and tied to the parts despatched.

**What about parts I make spare?**

Identify them or do not keep them: they enter another order without their history.

## Ejemplos

**A part fails and there are twenty mill certificates with no way to know which was theirs.**

- Records on the works order which heat each run was cut from

→ The matching certificate is identified in minutes.

**The client brought the material and nothing was recorded because «it was not ours».**

- Records the material identification even when the client supplies it

→ You can say which material was machined, which is what will be asked.

**Three spare parts are left on a shelf and used six months later.**

- Identifies spare parts with their works order, or does not keep them

→ No part enters an order carrying someone else's traceability.

**A part is touched up outside the normal flow and re-enters unrecorded.**

- Logs the rework as another operation, with its date

→ What was delivered and what was recorded match again.

**The client asks for the dimensional report and the gauge has no calibration record.**

- Records which instrument was used and when it was calibrated

→ The verification stands up to whoever reviews it.

**A delivery must be bounded and there is no record of which parts went on each note.**

- Records at despatch which parts and from which works order are included

→ Scope is limited to one delivery instead of the whole run.