Machine Design #86: Standard Material Names — One Material Should Not Have Five Names
Standard material name must remain clear, manufacturable, searchable, inspectable, and maintainable when the boundary changes.
Function before naming
Write the function, input, expected result, failure symptom, acceptance limit, and measurement method before selecting a name, mark, material, or note. Assign an owner to every value.
Core checks
- Grade, specification, and material condition: record value, source, method, owner, and pass/fail evidence.
- Local and supplier naming equivalence: record value, source, method, owner, and pass/fail evidence.
- Substitution rule and approval: record value, source, method, owner, and pass/fail evidence.
- Drawing, BOM, purchasing, and certificate match: record value, source, method, owner, and pass/fail evidence.
- Heat treatment or surface condition: record value, source, method, owner, and pass/fail evidence.
- Traceability and audit evidence: record value, source, method, owner, and pass/fail evidence.
| Failure mode | Symptom | Verification |
|---|
| Ambiguous identity | Wrong part or record | Search and audit a real lot |
| Omitted interface | Purchase, assembly, or service error | Walk the real route |
| Documents out of sync | Correct name, wrong revision | Baseline every reference |
Stating a material: five parts, and each missing part breaks its own thing
The material field in a title block has to answer five questions. Whichever one is missing, the shop fills in from habit, and the next batch may differ from the last.
| Part | Correct example | If it is missing |
|---|
| Grade | A6061, SUS304, S45C | "aluminium", "stainless", "steel" are families, not grades |
| Applicable standard | JIS H 4000, JIS G 4051 | The same designation can mean different things across standard systems |
| Condition or temper | A6061-T6, A5052-H32, SS400-D | A6061-O soft behaves nothing like A6061-T6; SS400-D differs from hot-rolled SS400 |
| Required hardness (if heat treated) | 60±2 HRC after hardening | The heat treater does not know where to stop tempering |
| Surface treatment and masked areas | black anodising, mask tapped holes | The coating changes sizes and the part no longer fits |
The four most common ways to get it wrong
| Written like this | The problem | Should be |
|---|
| "Aluminium" | Three alloy families differing in strength, weldability, formability and price | A5052-H32 or A6061-T6 or A7075-T6 |
| "Stainless" | Machining, welding and corrosion behaviour differ widely | SUS303 (heavy turning) or SUS304 (welding, forming) or SUS316 (aggressive corrosion) |
| "SS400" for a precision surface | Hot rolled, carries mill scale and residual stress, bows easily after machining | SS400-D where a bright surface and a more accurate blank are needed |
| "A6061" with no temper | The condition decides strength and bendability | A6061-T6 (strong) or a softer temper if it has to be bent |
Substitute materials: approve by table, not verbally
When the shop proposes a different grade because stock has run out, the decision has to rest on a sourced equivalence table, and the specific property the part needs has to be re-examined — not merely "it is also a tool steel". Some common tool steel grades:
| JIS grade | Equivalents | What must be preserved in a substitution |
|---|
| SKD11 | D2 (AISI), X210Cr12 (DIN) | Cold wear resistance and dimensional stability after hardening |
| SKH51 | M2 (AISI), HS6-5-2 (ISO/DIN) | Hot hardness — losing it removes the reason the grade was chosen |
Replacing SKH51 with SKD11 on a cutting tool changes exactly the property that led to the choice. This is why an equivalence table has to be paired with the question "which property does this part need", not just a sideways lookup of names.
Details of each grade are in the Materials series: #09 SS400 and SS400-D, #10 SUS303 and SUS304, #11 Aluminium A5052, A6061, A7075, #12 SKD11 and SKH51.
Material certificates: when they are needed and which kind
Writing the correct grade is only half. The other half is proving the stock really is that grade. On load-carrying, pressure-carrying or safety-related parts, a supplier's word does not replace a record.
| Level of certification | Content | Use when |
|---|
| Declaration of compliance | The supplier confirms the grade, with no measured data | Secondary parts, no load |
| Mill test report | Chemical composition and mechanical properties of that specific batch | Load-carrying parts, structural welded parts |
| Report witnessed by a third party | As above, with independent confirmation | Contract requirements, pressure equipment, regulated exports |
The point most often confused: a declaration of compliance is not a certificate with data. It says "correct grade" but gives no measured composition or properties for the batch being delivered. On a load-carrying part that is a large gap.
If the drawing does not state a certification requirement, the supplier will deliver the cheapest level — usually the lowest in the table. This is a requirement to be written down, not assumed.
Batch traceability: keeping the thread from stock to machine
When a material batch turns out to have a problem, the only question that matters is which machines are running parts from that batch. Answering it requires an unbroken thread:
- The batch number recorded on the stock at goods receipt.
- The batch number carried onto the parts as the stock is cut — by marking, a label, or a batch traveller.
- The batch number entered into the manufacturing record for the part.
- The part linked to the machine serial number in the delivery record.
A break at any step loses traceability. The step that breaks most often is the second: one bar is cut into several parts and the batch number stays on the offcut.
Which parts need traceability has to be stated on the drawing, because it brings marking and record-keeping work that the shop prices in. Demanding traceability on every part is an unnecessary cost.
Substitute material in an emergency
The machine is down, the correct grade is unavailable, and an equivalent grade sits in the stores. Three questions before agreeing:
- Which property is the governing one for this part? Strength, toughness, corrosion resistance,
dimensional stability, or weldability.
- Does the substitute preserve that specific property? Check a sourced equivalence table, not memory.
- Is the change temporary or permanent? If temporary, mark the part and record a date to replace it.
And write the decision on a change note. A verbal agreement on the shop floor at midnight is the surest way for nobody to know six months later what that part is made of.
MINATA release checklist
- [ ] Function, identity, boundary, and failure symptom are written.
- [ ] Ownership, interface, and mistake-proofing are clear.
- [ ] Six topic checks have evidence and pass/fail limits.
- [ ] Manufacturing, purchasing, inspection, and maintenance were tried.
- [ ] Revision, supplier, database, and lifecycle records agree.
Good engineering is an explicit chain that survives manufacture, operation, maintenance, and change. For standard material name, evidence that identification and function remain reliable is the MINATA standard.
Frequently asked questions
Is writing "A6061" enough?
Not yet. The temper has to go with it: A6061-O annealed and A6061-T6 solution treated and aged differ considerably in strength and bendability. Giving the grade without the condition leaves half the information blank.
What is the difference between SS400 and SS400-D?
The stock condition, not the grade. Hot-rolled SS400 carries mill scale, has a less accurate blank and needs machining allowance. Cold-finished SS400-D has a bright surface and a more accurate blank, so it can be used directly on unmachined faces — in exchange it costs more and needs care about bowing under asymmetric machining.
Is "stainless" acceptable?
Better not. SUS303 machines easily but does not suit welding; SUS304 welds and forms better but machines harder; SUS316 offers higher corrosion resistance. Writing "stainless" hands a design decision to the shop.
The shop asks to substitute a material because stock ran out. What then?
Approve it from a sourced equivalence table, and re-check the specific property the part needs — hot hardness, weldability, corrosion resistance or dimensional stability. Record the decision on the drawing or a change note; do not agree verbally on the shop floor.
Should the applicable standard be stated too?
It should, on important parts or when working across several standard systems. Writing S45C / JIS G 4051 is far clearer than S45C when the documents pass through several parties, and it avoids the same designation being read in a different system.
Frequently asked questions, continued
Is a declaration of compliance a material certificate?
Not sufficient for a load-carrying part. It confirms "the correct grade" but gives no composition or property data for the batch delivered. Load-carrying parts should require a mill test report with the data for that batch.
What happens if no certification requirement is stated?
The supplier delivers the cheapest level, usually the lowest. A certification requirement has to be written on the drawing or in the purchase order; it is never a default.
Where does batch traceability break most often?
At the cutting step. One bar is cut into several parts and the batch number stays on the offcut. Keeping the thread means transferring the batch number onto each part by marking, a label, or a batch traveller.
Should traceability be required on every part?
No. Traceability brings marking and record-keeping work that the shop prices in. Require it only where it is genuinely needed: load-carrying, safety-related, or regulated parts.
What has to be recorded when accepting a substitute in an emergency?
On a change note: the governing property of the part, the substitute grade and the source of the equivalence table, whether the change is temporary or permanent, and if temporary the date to replace it. A verbal agreement on the shop floor is the surest way for nobody to know six months later what the part is made of.
Conclusion
Standard Material Names is not paperwork done to make a file look tidy. It is how intent becomes a result that can be manufactured, assembled and measured repeatedly. A good drawing does not need the designer standing beside it to explain it; the structure of the information has to do that work.
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