Fasteners - Stud bolts - Part 1: Metric thread
1Key Takeaways
This specification defines the characteristics and markings of metric threaded steel, stainless steel, and non-ferrous metal threaded double-ended bolts.
2Expert Interpretation
This in-depth explanation of the technical requirements, dimensional specifications, material selection, and marking methods of the DIN 976-1 standard for metric threaded studs covers the latest standard updates, product classifications, tolerance requirements, and special provisions for stainless steel and non-ferrous metal applications, providing professional guidance for engineering design and procurement.
DIN 976-1 Standard Overview and Revision Background
DIN 976-1 "Studs for Mechanical Fasteners Part 1: Metric Threads" is a professional standard for studs issued by the German Institute for Standardization (DIN). The standard was developed by the NA 067-00-08 AA Special Working Group "Special Forms and Plastic Fasteners" under the Standardization Committee for Mechanical Fasteners (FMV). The latest version has undergone significant technical revisions compared to the December 2002 edition, reflecting the latest requirements of current engineering technology development.
Main Technical Changes to the Standard
The 2022 revised edition has comprehensively updated the standard. The main changes include:
| Changes | 2002 Edition | 2022 Edition | Technical Significance |
|---|---|---|---|
| Thread Tolerance | 6g | 8g (Strength Grade <8.8) | Relax manufacturing tolerance and improve production efficiency |
| Straightness Requirements | Product Grade A | Product Grade C | Adapt to a wider range of application scenarios |
| Length Marking | l | lc | Compared with DIN EN ISO 225 |
| Normative references | Old standards | Update to the latest version | Ensure the timeliness of technical requirements |
Scope of application and type classification of studs
This standard applies to studs with metric threads, made of carbon steel, stainless steel, and non-ferrous metals. They are divided into two main types based on the end form:
Form A: The thread end conforms to RL type (round end) according to DIN EN ISO 4753, with a maximum incomplete thread length of 2P (P is the pitch)
Form B: The thread end conforms to CH type (chamfered end) according to DIN EN ISO 4753, with an incomplete thread length also limited to 2P
Studs have a variety of applications. They can be used as bolts with nuts at both ends or as studs, offering extremely high application flexibility.
Dimensional specifications and tolerance requirements
The standard specifies the size series of studs in detail, covering metric thread sizes from M5 to M100. Key dimensional parameters include:
| Thread specification | Standard length range (mm) | Thread tolerance | Application areas |
|---|---|---|---|
| M5-M12 | 30-200 | 8g | General mechanical assembly |
| M16-M24 | 40-300 | 8g/6g | Heavy equipment |
| M30-M100 | 80-1000 | 8g | Large structural engineering |
Thread tolerance according to DIN ISO 965-2 medium level execution, ensuring interchangeability with standard nuts.
Material properties and strength grades
The standard specifies the corresponding strength requirements and mechanical properties for studs of different materials:
| Material type | Strength grade | Standard basis | Marking requirements |
|---|---|---|---|
| Carbon steel and alloy steel | 4.8, 5.6, 5.8, 8.8, 10.9, 12.9 | DIN EN ISO 898-1 | d≥5mm must be marked with strength grade |
| Austenitic stainless steel | A2-70, A4-70 | DIN EN ISO 3506-1 | d≥5mm Marking Steel Grade A2/A4 |
| Non-ferrous metal | According to material properties | DIN EN 28839 | No mandatory marking requirement |
Surface treatment and corrosion protection requirements
Depending on the application environment, studs can adopt a variety of surface treatment methods:
Electrogalvanized: Provide basic corrosion protection according to DIN EN ISO 4042
Non-electrolytic zinc flake coating: According to DIN EN ISO 10683, suitable for occasions with high strength requirements
Hot-dip galvanized: Provide the best corrosion protection according to DIN EN ISO 10684
Surface defect inspection is according to DIN EN 26157-1 (general requirements) and DIN EN 26157-3 (Particular Requirements) is implemented.
Product Identification and Color Coding System
The standard specifies a complete identification system, including mandatory strength grade identification and optional color coding:
| Strength Grade/Material | Color Identification | RAL Color Number | Application Description |
|---|---|---|---|
| Grade 5.6 | Chestnut Brown | RAL 8015 | General Structural Applications |
| Grade 5.8 | Gentian Blue | RAL 5010 | Machinery and Equipment |
| Grade 8.8 | Traffic Yellow | RAL 1023 | High Strength Requirements |
| Grade 10.9 | Pearl White | RAL 1013 | Ultra High Strength |
| Grade 12.9 | Traffic Black | RAL 9017 | Special High Strength |
| A2-70 Stainless Steel | Traffic Green | RAL 6024 | Corrosion Resistant Applications |
| A4-70 Stainless Steel | Fire Red | RAL 3000 | Highly Corrosive Environments |
Color marking shall not affect the assembly performance of the thread and shall use RAL 840-HR standard color card for comparison.
Inspection and Acceptance Criteria
Acceptance inspection of studs is carried out in accordance with DIN EN ISO 3269, including:
Dimensional inspection: Full-size inspection using calibrated thread gauges and calipers
Mechanical testing: Strength grade verification is completed using a universal testing machine
Surface quality: Visual inspection and surface roughness tester
Sampling plans are implemented in accordance with AQL standards to ensure consistent quality across batches of products.
Engineering application recommendations and implementation guidelines
When selecting double-ended studs in engineering design, the following points should be noted:
Material selection: Select carbon steel, stainless steel or non-ferrous metal according to the use environment, considering corrosion, temperature and strength requirements
Length calculation: The effective length of the stud should ensure sufficient engagement length, generally required to be 1-1.5 times the diameter
Preload control: Use a torque wrench or hydraulic tensioner to ensure the correct preload
Anti-loosening measures: In a vibrating environment, anti-loosening nuts should be used or thread lockers should be used
A complete quality control system should be established during the implementation of the standard, including incoming inspection, process control and final inspection, to ensure safe and reliable connections.
Coordination with other standards
DIN 976-1 is consistent with multiple international standards:
It is fully unified with ISO 225 in terms of dimensioning
Thread tolerances are coordinated with the ISO 965 series of standards
Mechanical performance requirements are aligned with European standards such as EN ISO 898-1
This coordination ensures the international applicability and interchangeability of the product, facilitating global procurement and equipment maintenance.