CN Quality Check
Standards Comparison Tool
EXECUTIVE SUMMARY
The query "gb/t805" resolves to GB/T 805-1988 扣紧螺母 (Prevailing-torque hexagon lock nuts) — a fastener product standard, NOT the steel-wire-rope series (Answer A's premise is incorrect). Answer B correctly identified the standard. Overall equivalence landscape: GB/T 805-1988 is a dimensional/mechanical product standard with no direct ISO/EN counterpart for the prevailing-torque nut type; closest international analogues are ISO 7042 / ISO 10513 (all-metal prevailing torque nuts). Procurement implication: buyers must specify prevailing-torque performance class and verify against ISO 7042/10513 test methods, as GB/T 805-1988 predates current ISO torque-test harmonisation.
APPLICABLE CHINESE STANDARDS
| Standard No. | Title (Chinese) | Scope | Mandatory/Recommended | Status |
|---|---|---|---|---|
| GB/T 805-1988 | 扣紧螺母 (Prevailing-torque hexagon lock nuts) | Dimensions, mechanical properties, prevailing-torque requirements for all-metal lock nuts | Recommended (GB/T) | Current (现行) |
| GB/T 3098.9-2020 | 紧固件机械性能 有效力矩型钢锁紧螺母 (Mechanical properties — Prevailing torque steel lock nuts) | Mechanical/torque performance for prevailing-torque nuts | Recommended | Current |
| GB/T 90.1-2023 | 紧固件 验收检查 (Fasteners — Acceptance inspection) | Sampling & acceptance | Recommended | Current |
| GB/T 90.2-2002 | 紧固件 标志与包装 (Fasteners — Marking and packaging) | Marking/packaging | Recommended | Current |
| GB/T 196-2003 | 普通螺纹 基本尺寸 (General purpose metric screw threads — Basic dimensions) | Thread dimensions | Recommended | Current |
STANDARD TIER CLASSIFICATION
| Standard | Tier | Description |
|---|---|---|
| GB/T 805-1988 | TIER 1 — Product Standard | Defines nut dimensions & prevailing-torque requirements |
| GB/T 3098.9-2020 | TIER 1 — Product Standard | Mechanical/torque performance |
| ISO 7042:2012 | TIER 1 — Product Standard | Prevailing torque hexagon high nuts |
| ISO 10513:2012 | TIER 1 — Product Standard | Prevailing torque hexagon nuts with flange |
| ISO 898-2:2022 | TIER 1 — Product Standard | Mechanical properties of nuts |
FLAG: Answer A applied GB/T 8050 (fibre ropes) — misapplication. GB/T 8050-2017 is 纤维绳索 (Fibre ropes), not steel wire ropes. Answer A's entire premise is void.
SCOPE BREAKDOWN
扣紧螺母 (Prevailing-torque hexagon lock nuts)
Chinese standard: GB/T 805-1988: 扣紧螺母 (Prevailing-torque hexagon lock nuts)
International equivalent: ISO 7042:2012 (Prevailing torque hexagon high nuts) — ⚠️ GB/T 805-1988 predates ISO 7042:2012; dimensional alignment partial
Equivalence: NEQ
Standard tier match: Both TIER 1 — valid comparison
Parameter comparison table:
| Parameter | Chinese Standard Value (Clause) | International Value (Clause) | Deviation | Mutual Recognition | Procurement Impact |
|---|---|---|---|---|---|
| Thread range | M6–M20 [Verify: GB/T 805-1988 §3] | M5–M36 (ISO 7042:2012 §4) | Narrower CN range | 附加测试后互认 (Mutual recognition after additional testing) | MEDIUM |
| Property class | Not specified in GB/T 805 [Verify: GB/T 805-1988 ~§4] | Class 8, 10, 12 (ISO 898-2:2022) | CN silent — must invoke GB/T 3098.9 | 不可互认 (Not mutually recognised) | HIGH |
| Prevailing torque (first removal) | ≥ specified min torque [Verify: GB/T 805-1988 ~§5] | Per ISO 2320 test method | Different test method (no direct comparison) | 附加测试后互认 (Mutual recognition after additional testing) | HIGH |
| Proof load | Per GB/T 3098.9-2020 | Per ISO 898-2:2022 | Method alignment partial | 附加测试后互认 (Mutual recognition after additional testing) | MEDIUM |
| Surface finish | Not specified [Verify: GB/T 805-1988] | Per ISO 4042 | N/A (only CN silent) | 不可互认 (Not mutually recognised) | LOW |
KEY DIFFERENCES SUMMARY
- Property class — GB/T 805-1988 does not define property class; ISO 7042 requires Class 8/10/12. Deviation: CN silent. 不可互认 (Not mutually recognised). Impact: HIGH.
- Prevailing-torque test method — GB/T 805-1988 vs ISO 2320. Different method. 附加测试后互认 (Mutual recognition after additional testing). Impact: HIGH.
- Thread size range — CN M6–M20 vs ISO M5–M36. CN narrower. 附加测试后互认. Impact: MEDIUM.
- Surface finish/coating — CN silent; ISO 4042 governs. 不可互认. Impact: LOW.
REGULATORY LINKAGE TABLE (法规联动)
| Compliance Scenario | Chinese Regulatory Basis | International Regulatory Basis |
|---|---|---|
| Mandatory product certification | None (fasteners not CCC-listed) | None (not CE-marked under CPR for general fasteners) |
| Engineering acceptance inspection | GB/T 90.1-2023 (Acceptance inspection) | ISO 3269 (Acceptance inspection) |
| Import/export compliance | CCIB commodity inspection (if applicable) | Destination customs + ISO 898-2 conformity |
| Designer/engineer obligation | N/A for product standard comparison | Local building/mechanical regulation |
AUDIT FLAG RESOLUTION
- 🔴 CRITICAL CORRECTION: Answer A misidentified GB/T 805 as steel wire ropes / GB/T 8050. GB/T 8050-2017 is 纤维绳索 聚丙烯裂膜、单丝、复丝（PP2）和高强度复丝（PP3）3、4、8、12股绳索 (Fibre ropes — Polypropylene split film, monofilament and multifilament PP2 and high-tenacity multifilament PP3 — 3-, 4-, 8- and 12-strand ropes). GB/T 8050-2026 is UPCOMING REPLACEMENT (即将实施, effective 2026-11-01). Answer A's steel-wire-rope comparison is void.
- ✅ RESOLVED: GB/T 805-1988 扣紧螺母 (Prevailing-torque hexagon lock nuts) — CURRENT (现行). No supersession.
- ⚠️ UNRESOLVED: GB/T 805-1988 §3 (thread range), §4 (property class), §5 (prevailing torque) — verify against official text.
PROCUREMENT VERDICT
- Confirm the intended standard is GB/T 805-1988 扣紧螺母, not GB/T 8050 (fibre ropes).
- Require supplier to declare property class per GB/T 3098.9-2020 (GB/T 805 is silent).
- Demand prevailing-torque test report per ISO 2320 for international acceptance.
- Verify thread range M6–M20 covers your application; larger sizes need alternate standard.
- Specify surface coating per ISO 4042 if corrosion resistance required.
- For EU/UK import, obtain ISO 7042:2012 conformity evidence.
REFERENCE DOCUMENT CHECKLIST (配套调阅清单)
- GB/T 805-1988 §3 — thread size range
- GB/T 805-1988 §4 — property class (verify if specified)
- GB/T 805-1988 §5 — prevailing-torque requirements
- GB/T 3098.9-2020 — mechanical properties
- ISO 7042:2012 §4 — dimensions
- ISO 2320 — prevailing-torque test method
FIELD INSPECTION CHECKLIST
- Verify nut marking (property class, manufacturer).
- Confirm thread gauge fit (M6–M20).
- Test prevailing torque on first removal.
- Check surface finish/coating uniformity.
- Verify packaging/marking per GB/T 90.2-2002.
CONFIDENCE RATING
🟡 MEDIUM — Standard identity resolved (GB/T 805-1988 扣紧螺母, CURRENT); Answer A's premise rejected. Core parameters flagged for official text confirmation (GB/T 805-1988 §3–§5).
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