JB/T 58651.7-1999

Quality inspection departments in fastener manufacturing companies use this standard to grade the quality of internally grooved cylindrical head screws, determining whether products are superior, first-class, or qualified. Purchasers and end-users also rely on this standard to evaluate and select screws of different quality levels. By providing a unified grading method and inspection requirements, this standard ensures comparability and consistency in fastener product quality, which is crucial for improving overall industry quality.

紧固件生产企业的质量检验部门使用本标准，对生产的内凹槽圆柱头螺钉进行质量分等，以确定产品属于优等品、一等品还是合格品。采购方和用户也可依据本标准评估和选择不同质量等级的螺钉产品。该标准通过统一的分等方法和检验要求，确保了紧固件产品质量的可比性和一致性，对提升行业整体质量水平具有重要意义。

This standard specifies the principles and methods for product quality grading of hexagon socket head cap screws and hexalobular socket head cap screws (collectively referred to as internal groove cylindrical head screws), adopting a three-level grading system: superior, first-class, and qualified. It applies to batches of single specification products accepted according to GB/T 90, and references the defect grades, weighted values, and unit defect score calculation formula from JB/T 58651.1. Quality grades are determined based on the sampling items, sampling plans, and defect weighted values in Table 1, along with the unit defect score criteria in Table 2, while Table 3 provides specific inspection methods and gauge requirements for each item.

本标准规定了内六角圆柱头螺钉和内六角花形圆柱头螺钉（统称内凹槽圆柱头螺钉）的产品质量分等原则和方法，采用优等品、一等品、合格品三级分等体系。标准适用于按GB/T 90验收的单一规格产品批，并参照JB/T 58651.1总则中的缺陷等级、加权值和单位缺陷分计算公式。通过表1规定的抽查项目、抽样方案和缺陷加权值，以及表2的单位缺陷分标准进行质量等级判定，表3则列出了各项目的具体检验方法和检具要求。