What an audit is for
An audit answers one question: will this plant repeat what its sample showed? A good sample proves that the plant can make a good bearing once. An audit looks for the systems that make it repeatable, such as incoming checks, controlled heat treatment, calibrated gauges and records that connect a finished lot to its materials and settings.
It is useful to separate three kinds of review. A document review can be done remotely and covers certificates, procedures and sample records. A remote walk-through by video shows the floor and lets you ask questions in real time. An on-site audit adds the ability to open drawers, check gauge labels and follow a real lot through the plant. Match the effort to the volume at stake; a first pilot lot rarely justifies more than the first two.
Before the visit: documents to request
Ask for these items in advance, so the visit is used for verification, not for collecting paper:
- Business licence and a description of what is made in-house and what is bought in.
- Quality system certificates, such as ISO 9001, and IATF 16949 if you buy automotive parts. Check the scope and the expiry date on the certificate; certificates belong to the plant and are verified per project.
- A process flow chart for the product family and a list of the main machines.
- Inspection records for a recent lot of a similar designation.
- Gauge calibration schedule and a list of measuring equipment.
- The plant's approach to nonconforming product and customer complaints.
Walking the process
Follow the material, not the guide. The table lists the stations that matter and what to ask at each.
| Station | What to look at | Evidence to request |
|---|---|---|
| Incoming steel | Bar or tube storage, identification, supplier list | Mill certificates, incoming checks |
| Forging and turning | Ring blanks, tooling condition, scrap control | First-piece and in-process checks |
| Heat treatment | Furnace controls, quench, tempering | Hardness records, furnace logs |
| Grinding and honing | Raceway and bore finish, wheel dressing | Roundness and surface checks |
| Balls, rollers, cages | Own production or purchased; lot control | Supplier records, ball grade under ISO 3290 |
| Cleaning and assembly | Washing, clean areas, grease dosing | Cleanliness and noise checks |
| Final inspection and packing | Sampling plan, rust protection, labelling | Final inspection report, pack spec |
The process itself is described on the production process page.
Gauges, calibration and the lab
A plant is only as good as its measurement. Look at the gauges used at each station: are they labelled with a calibration date, are they stored properly, and does the operator know the tolerance? Ask to see the instruments for bore, outside diameter, width, roundness and radial clearance, and the hardness tester. Ask when each was last calibrated and by whom. Where noise matters, ask how the vibration test is set up and how the reference piece is controlled, because vibration results mean little without a stable reference.
A small lab with a hardness tester, a roughness meter and a microscope does not prove quality, but its absence on a plant that claims precision output is a flag. The measurement items are discussed in testing and inspection.
Traceability and records
The strongest sign of a controlled plant is that it can follow a finished lot back to its inputs. Choose a lot from the last month and ask for its batch card. You should be able to see the steel heat or bar lot, the heat treatment batch, the grinding shift and the assembly date, plus the final inspection result. If the plant can produce this within minutes, it keeps records as a habit. If it takes hours or the records look newly written, treat the system as weak.
Ask also how marks on the bearing relate to the batch. A batch code or date code on the ring or the box is the link that makes later complaints solvable, as discussed in counterfeit bearing risks.
Questions for management and the quality team
The floor tour shows equipment; the conversation shows how decisions are made. Put these questions to the quality manager and the sales lead, and note whether the answers agree.
- What share of this product family is made in-house, and which operations are subcontracted? Ask especially about rings, balls and cages.
- What is the plant's typical monthly output for this designation, and what share of capacity would our order use?
- How are customer changes to cage, grease or clearance handled and documented?
- What happens to a lot that fails final inspection: rework, regrade or scrap, and who decides?
- How many complaints were received in the last year for this product family, and what was done about them?
- Which customers can be named as references without breaching confidentiality? An answer such as an industry sector is often enough.
Clear, consistent and slightly critical answers are a good sign. Defensive or vague answers, or claims that nothing ever fails, usually mean the plant does not measure its own problems.
Adjusting the checklist by product
The same list needs small changes for different bearings. For small deep groove and miniature types, pay more attention to cleanliness, grease dosing and the noise test, because users hear defects. For tapered and cylindrical roller types, look at roller grinding, matching of cone and cup sets, and the gauging of internal setting. For housed units and agricultural lines, look at casting quality, seal fit and the greasing process, as these products fail through dirt and water, not through fatigue. For automotive programs, add a review of change control and product identification, because auditors in that sector will expect them.
Red flags worth noting
- Different answers from different staff on what is made in-house.
- Gauges with no calibration labels, or inspection records that are all identical.
- Finished goods stored open to the air, with rust visible on stock.
- Reluctance to show the heat treatment area or the final inspection bench.
- Certificates that cover a different address or product range.
- A sample that is clearly better made than anything on the production floor.
Scoring and follow-up
Keep the audit simple. Score each station as acceptable, needs action or unacceptable, write down what you saw, and list the actions with dates. Share the report with the plant and agree corrective steps. A plant that responds seriously to findings is often a better partner than one that scores perfectly on the first visit, because it shows it can improve.
The desk can arrange and attend audits, collect the documents above and report findings in a common format. For routine supply, the audit is followed by pre-shipment checks described in pre-shipment bearing inspection. To discuss a project, use the quote form, and see quality control for the broader process.