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العربية Made-to-drawing fasteners fail most often when the drawing shows shape and size, but not enough material detail. A supplier may produce the correct geometry, yet use the wrong steel grade, heat treatment, coating, or certificate level.
For buyers and engineers, the material requirement must be written as clearly as the dimensions.
Why Material Details Matter
A custom bolt, stud, pin, anchor, or special nut is usually designed for a specific load, environment, or assembly method. If the material is vague, performance becomes uncertain.
| Missing Requirement | Possible Result |
|---|---|
| Material grade | Wrong strength or corrosion resistance |
| Heat treatment | Low hardness or brittleness |
| Coating requirement | Rust, poor thread fit, or galling |
| Test standard | Disputed inspection result |
| Certificate type | Project or customs delay |
For special drawings, buyers should start with a clear custom fastener service request instead of treating the part like a standard catalog item.
Core Material Requirements to Specify
Material Grade and Standard
Do not write only “carbon steel” or “stainless steel.” Use a recognized grade and standard where possible.
| Material Type | Common Examples | Typical Use |
|---|---|---|
| Thép carbon | Q235, C45, ASTM A307, ASTM F1554 | General construction, anchors |
| Alloy steel | 35CrMo, 42CrMo, ASTM A193 B7 | High-strength or high-temperature use |
| Thép không gỉ | 304, 316, A2-70, A4-80 | Corrosion-resistant applications |
| Brass / copper alloy | C360, H62 | Electrical or decorative parts |
| Special alloy | Inconel, Monel, titanium | Chemical, marine, high-temperature service |
For common options, review carbon steel fasteners and stainless steel fasteners before approving the drawing.
Heat Treatment and Mechanical Properties
Strength Must Be Measurable
If the part carries load, specify mechanical properties. Material name alone is not enough.
Include:
- Tensile strength or property class.
- Yield strength or proof load.
- Hardness range.
- Impact test requirement, if used in low temperature.
- Heat treatment condition, such as quenched and tempered.
- Applicable test standard, such as ISO, ASTM, SAE, or EN.
For load-critical parts, compare the requirement with high-strength fasteners to avoid under-specification.
Coating and Environment
Finish Must Match Service Conditions
Coating should be selected after checking exposure, thread fit, and installation method.
| Environment | Suitable Finish |
|---|---|
| Indoor dry use | Plain, black oxide, zinc plated |
| Outdoor construction | Hot-dip galvanized, zinc flake |
| Marine or chemical exposure | 316 stainless steel, PTFE, special alloy |
| High-strength electroplated parts | Confirm hydrogen embrittlement control |
For finish selection, see various coated fasteners.
Final Buyer Checklist
Before production, confirm:
- Latest drawing revision.
- Exact material grade and standard.
- Mechanical property requirements.
- Heat treatment process.
- Coating type and thickness.
- Test report and MTC requirements.
- Batch traceability and packing labels.
Made-to-drawing fasteners should never rely on “equivalent material” unless the engineer approves it in writing. Clear material requirements protect the buyer, the supplier, and the final assembly.