The new standard introduces a more structured and detailed approach to marking fasteners, replacing the previous system that was often confusing. It consists of eight key elements, including surface treatment of the separator. Under the new standard, the product name and its corresponding standard details are refined into multiple items. The numbering of products is separated by spaces, while specifications and sizes align with the accuracy of the old standard, using a multiplication sign (×) to separate dimensions. Other characteristics or diameters, as well as nominal length and thread length, are indicated by a short dash (-). This distinction helps differentiate between the new and old standards, where the old one focused on refining the standard number and other specific requirements.
In the new system, the separation between the old and new standards is clearer—only the thread length or rod length is separated by a dash, which helps avoid confusion in wrenching styles. Additionally, numbers in the marking include both the size and subsequent details. Previously, under the old standard, product markings were often ambiguous. The new standard also clearly states that the product name cannot be omitted, though partial omission is allowed in certain cases, unlike the old standard which permitted more flexibility.
This revision also covers cylindrical pins, cotter pins, and rivets. The marking examples now clarify that the nominal diameter of fasteners refers to their outer diameter, and the nominal shape of conical pins has been adjusted. New examples have been added to cover a wider range of fasteners, including bolts, pins, screws, nuts, washers, and self-tapping screws. The new standard provides more comprehensive information, such as the outer diameter (D) for screws, the shaft diameter (d0) for bolts and pins, and the retaining ring diameter (d), among others.
There are 16 additional examples of diameters or features, covering almost all types of fasteners. These examples focus on the external thread size or nominal size, making the marking more representative and easier to understand. For instance, the rod diameter of a bolt or the outer edge of a washer is clearly defined, aiding in the interpretation of standard provisions. The f4 marking method for diameters, holes, or shaft retaining rings, along with rod diameter tolerance, should be included if required by design, ensuring a complete fastener marking that includes all relevant characteristics.
Nominal length items, such as category, standard number, thread size, or nominal size, are clearly defined. To avoid confusion, especially when marking different types of fasteners like pins, rivets, or rods, the use of letters is essential. The length of bolts and screws, excluding the head, is referred to as the "nominal length." For example, the overall length of a countersunk bolt or anchor bolt includes the head, and this is considered the nominal length. In some cases, only the general category is mentioned, such as "bolt" or "screw," without specifying the exact type.
For hexagon head bolts or square head bolts, the length is already considered the nominal length, so no additional marking is needed. The length of split pins is also marked as the nominal length. The standard number in the marking is always included to ensure clarity and consistency across applications. Overall, the new standard improves accuracy, reduces ambiguity, and ensures better communication in fastener specifications.
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