Free Fishbone Diagram Template

Use a small cross-functional group that knows the process and can retrieve evidence: the process owner, operator or team lead, quality, maintenance or tooling, inspection, and supplier quality when incoming material or outside processing is involved. Do not fill the session with observers; include people who can explain the work and check records after the meeting.

1. Step 1

   Define the problem clearly

   Start with the Problem / Effect Definition section. Record the issue ID, customer or internal source, part number, lot or batch, where the issue was made, where it was found, the affected quantity, suspect quantity, containment status, and requirement source.

   The most important field is the problem statement. Write what happened in factual, measurable terms. Do not include the assumed cause. A good problem statement says what was found, where it was found, how many parts were affected, and what requirement was not met.

   Problem statement example

   Internal inspection found A-214 support plates from A214-LOT-0718 (WO-2026-7812) with the OP-30 hole measuring 8.18–8.23 mm against drawing DRW-A-214 Rev F requirement of 8.00 +0.05/-0.00 mm. Thirty-six plates were affected and 120 plates were suspect under NCR-2026-119.

   Avoid:

   Operator drilled the hole too big.

   The weak version assumes the root cause before the team has checked the evidence.

   Problem / Effect Definition

   

2. Step 2

   Add the problem to the fishbone worksheet

   Next, write a short version of the problem in the box at the head of the fishbone diagram. This keeps the team focused on one clear issue. For example, use "OP-30 hole oversize at 8.18–8.23 mm on A-214 support plates found at internal inspection" rather than "operator error" or "drilling issue."

   Once the problem is written, use the category branches to capture possible causes. Write each branch as a testable possibility, not an accusation or an action.

3. Step 3

   Brainstorm possible causes under each area

   Work through the six areas one at a time: People, Method / Process, Machine / Equipment, Material / Supplier, Measurement / Inspection, and Environment.

   Do not try to prove a root cause in the meeting. Use the six areas to surface cause paths that deserve evidence checks. Ask questions such as:

   • Was the operator trained on the latest revision?
   • Was the work instruction clear?
   • Was the drill, bushing, fixture, gauge, or machine condition within its defined limits?
   • Was the material from the correct source, lot, and specification?
   • Should inspection have caught the issue?
   • Did lighting, layout, storage, temperature, or workload contribute?

   Write possible causes, not fixes. "PM-DRILL-08 may not require a bushing wear limit check" is a possible cause. "Add a bushing wear check" is a corrective action and belongs later.

4. Step 4

   Move the strongest causes into the cause review table

   After the brainstorm, choose the strongest possible causes and transfer them into the Cause Review table. Use the Cause Review table to separate a brainstormed cause from one that is supported or still open. The team records the category, evidence needed, evidence result, priority, next step, and notes.

   Do not remove weak or contradicted ideas from the record too early. If evidence rules something out, mark it as contradicted. That shows the team considered it and prevents the same debate from coming back later.

   Cause Review

   

5. Step 5

   Assign evidence, owners, and due dates

   Assign an evidence check, owner, and due date to each prioritized possible cause. Evidence may include the actual part, returned sample, inspection record, work instruction, training record, batch certificate, maintenance record, test result, photo, measurement, or supplier response.

   Use clear evidence wording. "Check the tooling" is weak. "Review bushing wear photo EVD-119-03, measurement log EVD-119-01, and PM-DRILL-08 Rev B" is stronger.

6. Step 6

   Decide what investigation comes next

   Use the Investigation Next Steps section to turn the fishbone session into follow-up work. Record the cause path to investigate next, the evidence still needed, the owner, the due date, and the related 5 Whys, 8D report, non-conformance report (NCR), corrective action request (CAR), or supplier corrective action request (SCAR) reference.

   This section does not authorize corrective action. It records the handoff from the brainstorm to the formal investigation.

   Investigation Next Steps

   

7. Step 7

   Close the session with checks

   Before closing the fishbone session, confirm that the problem statement is factual, possible occurrence-cause paths and possible escape/detection weaknesses have both been considered, evidence checks are assigned, open and ruled-out paths are identified correctly, and the next investigation has an owner and due date.

   Common Mistakes and Closeout Checklist