GB/T 1228, GB/T 1229, GB/T 1230, GB/T 1231, GB/T 3632 and DIN 6914 are often mentioned together in structural bolting discussions, but they do not all cover the same article. Some describe a bolt, some a nut or washer, some a complete assembly and some a particular tightening system.
Specifying the correct standard starts by identifying what is being purchased: a single bolt, a nut, a washer or a matched set. A standard number alone does not prove interchangeability with another standard.
What does each standard cover?
| Standard | General scope | What the purchaser still has to confirm |
|---|---|---|
| GB/T 1228 | High-strength large hexagon head bolts | Grade, dimensions, marking and the mating nut/washer |
| GB/T 1229 | High-strength large hexagon nuts | Nut grade, dimensions and matching bolt assembly |
| GB/T 1230 | High-strength plain washers | Washer dimensions, grade and matching assembly |
| GB/T 1231 | High-strength large hexagon bolt-nut-washer assemblies | Assembly grade, marking, test and tightening requirements |
| GB/T 3632 | Torsional shear type high-strength bolt-nut-washer assemblies | The complete TC system, installation method and inspection |
| DIN 6914 | High-strength hexagon head bolts with large across flats for structural steel bolting | The product grade, dimensions and the mating DIN components |
The first four GB/T standards are related but not identical in scope. A bolt made to the bolt standard is not automatically a complete assembly. GB/T 3632 describes a tension-control system, so the nut, splined end and installation procedure are part of the product definition.
Is DIN 6914 equivalent to GB/T 1228?
They may both describe a large hexagon head structural bolt, but that does not make them automatically interchangeable. Dimensions, tolerances, material grades, marking and the associated nut and washer can differ. A project that specifies DIN 6914 may require a different assembly and documentation package from one that specifies GB/T 1228–1231.
Do not accept “DIN 6914 equivalent” as a substitute for a project approval. The drawing, the project specification and the engineer's acceptance criteria decide whether a substitution is allowed.
What changes between a bolt and a bolt set?
A bolt set normally includes the bolt, nut and washer as a matched assembly. The set may have its own grade, marking and test requirement. Buying the three items separately can produce a collection of correct-looking parts that has not been qualified as a set.
For a TC assembly, the set is even more tightly defined: the bolt end, nut and tightening method work together. Replacing one component with a similar item can change the installation behaviour.
What should the RFQ say?
State:
- The standard and edition or year.
- Whether the item is a bolt, nut, washer or complete set.
- The property class or grade.
- The diameter, length and thread length.
- The required dimensions and tolerances.
- The marking and traceability requirement.
- The surface finish.
- The test and inspection requirements.
- The installation method for a TC or other tension-control system.
- Whether an alternative standard is permitted, and who approves it.
Common mistakes
- Treating GB/T 1228 as a complete assembly standard. It is not the same scope as a bolt-nut-washer set.
- Assuming DIN 6914 and GB/T 1228 are interchangeable. The project must approve any substitution.
- Buying a TC bolt without the matching nut and installation method. The system is the product.
- Using the standard number without the grade. A standard does not replace the property class.
- Ignoring marking. The marking is how the delivered batch is checked against the order.
- Accepting a certificate for a different diameter. The document must cover the supplied item.
Tangtie's standard-related supply scope
Tangtie supplies high-strength structural bolt sets and torsional shear bolt sets. The applicable standard, grade, marking and document package are confirmed on the approved drawing or order. A reference to a standard on this website is not a claim that every possible size or grade is certified to it.
Next step: send the standard, grade, assembly scope and drawing to request a quote. The reply should separate the standard reference from the actual product approval and inspection package.
This note is general technical guidance prepared for the product library. It is not a project-specific approval and does not replace the specification issued by the project engineer. Values requiring test evidence are not published.
