Short answer
Don't try to document everything. Find the few operations where losing one person would hurt quality or output, watch the expert do the job, and write down the key points and the reasons behind them, not just the steps. Put it on a one-page setup sheet, have someone else run the job from it, fix what they trip over, and put it under document control.
Where tribal knowledge hides
It is rarely in the steps everyone can see. It's in the small decisions an experienced person makes without thinking:
- The order they tighten clamps, and how hard.
- The offset they apply after a tool change, or on the first part of a new bar.
- Which machine they quietly avoid for a particular job, and why.
- The sound, chip colour or surface that tells them a tool is going.
- The feature they always check twice because it caused a return once.
- The workaround for a drawing that doesn't quite match how the part is really made.
Decide what to capture first
Score each critical operation on two things, from 1 to 3: how much it would hurt if the expert were away for a month, and how few people can do it well. Multiply them. Start with anything that scores 6 or 9.
| Operation | Impact if missing | People who can do it | Priority |
|---|---|---|---|
| 5-axis setup, housing | 3 | 3 (one person) | 9 |
| Grinding, final diameter | 3 | 2 (two people) | 6 |
| Saw cut-off | 1 | 1 (most of the shop) | 1 |
The examples are illustrative. Use your own scrap, rework and delivery data to score impact, not opinion.
How to capture it: steps, key points and reasons
The most reliable method is still the one developed for wartime training in the 1940s, Training Within Industry's Job Instruction. Break the job into three layers:
| Layer | What it is | Example |
|---|---|---|
| Important step | A logical stage that moves the job forward | Load the part in the fixture |
| Key point | Anything that makes or breaks the step: quality, safety or "the knack" | Seat it against both locating pins before clamping |
| Reason | Why the key point matters | A part off one pin shifts the bore position by 0.1 mm and fails on the CMM |
The reasons are what most documentation leaves out, and they are what lets the next person make the right call when something is slightly different from last time.
- Watch, don't interview. Experts skip what they no longer notice. Watch the job, ideally on video, and ask "why did you do that?" at each pause.
- Capture the first-part routine. Setup and the first part after a change are where most knowledge lives and most scrap happens.
- Use photos of the real setup, with the key points marked on them.
- Keep it to one page per operation where you can. A document nobody opens has captured nothing.
What a good setup sheet contains
- Part number, revision and operation number, and the machine it runs on.
- Fixture, workholding and tooling list, with tool lengths or offsets where they matter.
- Program name and revision.
- A photo of the setup with locating points and clamp sequence marked.
- The key points and reasons for the steps that cause scrap.
- First-part checks: which features, which gauge, and what to adjust if they're off.
- In-process checks and their frequency.
Prove it works
The test of a captured method is simple: someone who has never run the job sets it up from the document alone while the expert watches and says nothing. Every question they ask is a gap in the document. Fix it, then repeat with another person.
Keep it alive
Captured knowledge decays the moment the method changes and the sheet doesn't. Put setup sheets and work instructions under document control, make updating them part of any process change, and review the critical ones when you review scrap. ISO 9001 asks for exactly this under organizational knowledge, clause 7.1.6.
Frequently asked questions
What is tribal knowledge in manufacturing?
Process knowledge that lives in people's heads rather than in documents: settings, sequences, workarounds and judgement calls that experienced operators and setters use but have never written down.
What is the difference between an SOP, a work instruction and a setup sheet?
An SOP describes a process at a high level: who does what and when. A work instruction describes how to perform one task step by step. A setup sheet is a specific work instruction for setting up one operation on one machine, with tooling, offsets and first-part checks.
How long does it take to document a critical operation?
Observing and drafting one setup typically takes a few hours, plus validation runs with another operator. Starting with the two or three highest-risk operations gets most of the benefit quickly.
Does video replace written instructions?
Video is excellent for capturing and teaching technique, but it is hard to search, update and control. Use it alongside a short written sheet that carries the key points, reasons and checks.