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ISO (International Organization for Standardization) is a global organization composed of national standards bodies from around the world. International standards are typically developed through ISO technical committees, and any member country can participate in a committee if they have an interest in its projects. Additionally, government and non-governmental international organizations related to ISO may also take part in this standardization process. ISO works closely with the International Electrotechnical Commission (IEC), especially in the field of electrical standardization.
The drafting of international standards follows the procedures outlined in the ISO/IEC Guide, Part 2. Once a draft is approved by a technical committee, it is circulated for voting among all participating groups. For an international standard to be officially published, at least 75% of member bodies must vote in favor.
ISO 898-1 was developed in collaboration with ISO/TC2/SC1, the Subcommittee on Mechanical Performance of International Standardized Fasteners, as well as CEN/TC 185. The standard includes terms, chapters, tables, diagrams, and appendices that define the mechanical properties of fasteners.
**ISO 898 carbon steel and alloy steel fastener machinery consists of five parts:**
- Part 1: Mechanical properties of coarse and fine threaded bolts, screws, and studs
- Part 2: Guaranteed load of coarse threaded nuts
- Part 5: Tightening screws and similar threaded fasteners without tensile strength
- Part 6: Guaranteed load of fine threaded nuts
- Part 7: Torque test of bolts and screws for nominal diameters M1–M10
This revision refers to the first part of the standard.
a. The standard defines the mechanical properties of bolts, screws, and studs made from carbon or alloy steel tested at ambient temperatures between 10°C and 35°C. The mechanical and physical properties listed in the standard are measured at room temperature, but these properties may change when tested at higher or lower temperatures. An impact performance test is specified at -20°C.
b. The operating temperature range for fasteners is from -50°C to +150°C. If the user selects a temperature below -50°C or above +150°C, up to +300°C, it should be noted that temperature changes can affect the mechanical and physical properties. As temperature increases, yield strength or non-proportional elongation stress decreases, reducing overall strength. At +300°C, the failure load is calculated based on tensile test results, regardless of the type of loading. However, when the temperature exceeds -50°C, the influence of ambient conditions on strength and ductility must be considered. At temperatures above +300°C, failure modes may include loosening and creep, leading to significant elongation or breakage even at lower stress levels. Therefore, this standard does not cover performance requirements for temperatures above +300°C (+250°C for grade 10.9). Similarly, at temperatures below -50°C, most steel grades become brittle, reducing strength, ductility, and impact resistance.
c. Low-strength fasteners are often produced using cold forging processes such as precision screw machines, heading machines, and cold heading machines, many of which are certified under ISO quality management systems. This standard highlights that cold-hardened fasteners (grades 4.8, 5.8, 6.8) are more affected in terms of joint strength, cold-brittle stress, and toughness compared to heat-treated fasteners.
d. For low-temperature applications beyond the standard's operating range, the following standards are recommended:
- EN 10269: "Steel and nickel alloys for fasteners for high or low temperature performance"
- ASTM F2281: "Standard Specifications for Stainless Steel and Nickel Alloy Bolts, Hex Head Screws and Studs for Heat and High Temperature Equipment"
- ASTM A320: "Alloy Steel Bolts for Low Temperature Service"
e. ISO 898-1 applies to bolts, screws, and studs regardless of head shape—such as hexagonal, square, hex socket, slotted pan, T-head, etc. However, for certain head geometries where the shearing area of the head is smaller than the thread stress cross-sectional area, or where the thin waist section is insufficient, the fastener may not meet the tensile or torque requirements specified in the standard. Specific testing and evaluation methods are provided for such cases, including countersunk heads, semi-recessed heads, and thin-waisted fasteners.
**Fasteners covered by this standard:**
- Made from carbon steel or alloy steel
- Metric threads conforming to ISO 68-1
- Compatible with coarse threads M1.6 to M39 and fine threads M8×1 to M39×3
- Diameter and pitch combinations according to ISO 261 and ISO 262
- Thread tolerances and fits in line with ISO 965-2 and ISO 965-4
**This standard does not apply to:**
- Set screws and other similar untensioned threaded fasteners
- Weldability, corrosion resistance, shear stress resistance, and fatigue resistance
**Relevant information:**
Wang Weiwu: Discussing the new version of ISO 898-1:2013
The new version of the ISO nut technology standard, ISO 898-2:2012, introduces ten major changes.