What a Tool Change Actually Costs — Records Before Geometry
A tool is qualified as a geometry, not as a supplier
When a process is approved, what is approved is a specific cutting geometry running inside a specific window. That has three consequences that surprise buyers:
- Same drawing, different cutter, new evidence. Two tools that share a nominal diameter but differ in rake, margin or edge prep do not cut the same hole. A change of geometry is a change of process even when the part number does not move.
- The record has to be reproducible, not impressive. A tool-life figure from one favourable run is worth less than a modest figure held across several batches, because the second one predicts what the next batch will do.
- Requalification scope is negotiable; the fact of it is not. Whether a change needs a full first-article or a reduced comparison depends on the customer and on what changed. That scope is worth agreeing before the tool is made, not after.
The sample and first-article steps themselves are described on Sample Validation Process. This page does not repeat them; it addresses what a tool record contains and how a change is scoped.
What a tool record should be able to answer
| Question asked later | What the record has to hold | Where it comes from |
|---|---|---|
| Which tool made this part? | Batch identification that resolves to a drawing revision and a manufacturing date | Agreed at order, marked on the package |
| Is it the geometry that was approved? | Nominal geometry drawing with the revision the part was approved against | Frozen at first-article, not reissued silently |
| Has this tool drifted? | Measured geometry at defined points, and the inspection method used | Inspection plan agreed per project |
| How long did it last? | Life expressed in a unit both sides use — holes, parts or metres — and the failure mode observed | Trial and production feedback |
| What changed, and when? | A change log with the reason, not only the date | Maintained per tool, not per order |
Three levels of change, three sizes of evidence
| What changed | Typical evidence scope | Note |
|---|---|---|
| Coatings or substrate on an unchanged geometry | Comparison run on the same part, same window | Cheapest to justify; still needs the comparison, not an assertion |
| Edge prep or margin, same nominal dimensions | Hole-quality comparison plus a life comparison | The usual case, and the one most often under-documented |
| Rake, flute count or step geometry | Full first-article against the part drawing | This is a new process; treat it as one |
These are the scopes we see most often, not a rule that overrides your customer's quality plan. Where the plan is stricter, the plan wins.
The honest boundary on evidence
- We do not publish a certification claim. If your plan requires a specific approval, say so on the RFQ and we confirm what can and cannot be supported before a quote is issued.
- Workshop images are resources, not results. Grinding, laser and inspection equipment show capability to make a tool; they do not prove a tolerance, a tool life or a cycle time. That framing is set out on Manufacturing & Quality Evidence and it applies here too.
- No invented numbers. Where a figure is not from a real run on a real part, it is not written down. Where a value is pending, it is marked pending rather than estimated.
Boundaries, so you do not read the wrong page
- The sample and first-article sequence → Sample Validation Process.
- Fastener hole quality and stacks → Aerospace Fastener Hole Machining.
- Casing and seal bores → Aerospace Engine & Actuation Bores.
- General programme-level framing — qualification lock, stack mismatch → Aerospace & Defense hub.
What to send so the evidence scope can be quoted with the tool
- The approved geometry drawing, if a tool is already qualified on this part
- Your customer's quality plan requirement, quoted rather than summarised
- What you want to change, and the defect or cost that motivates it
- How tool life is measured today, and in what unit
- Batch size and whether a comparison run is possible on a real part
- Which records must travel with the parts, and in what format
Quick answers before you RFQ
Can you reverse-engineer a tool from a qualified sample?
Usually yes, and it is a normal starting point rather than an exception. Send the sample with the part print and the qualified window. What we will not do is claim the copy is dimensionally identical without measuring it, so the geometry is reported back before any batch is made.
Do you provide first-article documentation?
We provide the measured geometry and the inspection record agreed for the project, and we work to the acceptance criteria you specify. We do not issue a certificate we are not accredited to issue — if your plan requires one, that requirement is raised and confirmed at RFQ stage so nobody discovers the gap after the tool is made.
How is tool life reported?
In the unit the shop already uses — holes, parts or metres — with the failure mode stated. A number without a failure mode is not useful, because a tool that fails by chipping and a tool that fails by wear call for different corrective actions.
Is this the same as the sample validation page?
No. Sample Validation Process describes the steps of proving a tool on a part. This page describes what a tool record has to contain and how much evidence a given change requires — which is the question that comes up after the tool is already approved.
Send the approved geometry and the quality plan requirement
Scope of evidence is quoted with the tool, not added afterwards. Where a certification or approval is required, it is confirmed before a price is issued.