QC/T 1257-2025 Hexagon flange removing scraps and grounding bolt English, Anglais, Englisch, Inglés, えいご
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ICS
T
Professional Standard of the People's Republic of China
QC/T 1257-2025
Hexagon flange removing scraps and grounding bolt
汽车用六角法兰面自排屑接地螺栓
(English Translation)
Issue date: 2025-12-17 Implementation date: 2026-07-01
Issued by the Ministry of Industry and Information Technology of the People's Republic of China
Contents
Foreword
1 Scope
2 Normative References
3 Terms and Definitions
4 Type Dimensions
5 Technical Requirements
6 Product NumberingHexagon Flange Bolts for Automotive Use
7 Product Numbering
Hexagon Flange Self-Cleaning Grounding Bolts for Automotive Use
1 Scope
This document specifies the type dimensions, technical requirements, and product numbering for hexagon flange self-cleaning grounding bolts (hereinafter referred to as "bolts") with nominal thread diameter d=6 to 10.
This document applies to grounding connection points on all-steel vehicle structures, such as various automotive electrical system components including powertrain grounding harnesses, capacitor grounding harnesses, and instrument panel grounding harnesses.
2 Normative References
The contents of the following documents constitute essential provisions of this document through normative reference. For dated references, only the edition corresponding to the date applies. For undated references, the latest edition (including all amendments) applies.
GB/T 90.1 Fasteners — Inspection and Acceptance
GB/T 90.2 Fasteners — Marking and Packaging
GB/T 196 Basic Dimensions of General Purpose Metric Threads
GB/T 197 General Purpose Metric Screw Threads — Tolerances
GB/T 3098.1 Mechanical Properties of Fasteners — Bolts, Screws and Studs
GB/T 3103.1 Fasteners — Tolerances — Bolts, Screws, Studs and Nuts
GB/T 5779.1 Fasteners — Surface Discontinuities — Bolts, Screws and Studs — General Requirements
GB/T 30512 Requirements for Prohibited Substances in Automobiles
QC/T 326 Product Numbering Rules for Automotive Fasteners
QC/T 625 Coatings and Chemical Treatment Layers for Automotive Use
QC/T 863 Weld-on Square Nuts
3 Terms and Definitions
The following terms and definitions apply to this document.
3.1 grounding
Grounding refers to connecting a circuit, device, or subsystem to a reference ground, with the purpose of providing an equipotential point or surface. The reference ground for automotive electronic systems is the vehicle frame or body, with the battery negative terminal directly connected to the frame or body.
3.2 grounding bolt
A grounding bolt is a connecting bolt between the grounding point of a circuit, device, or subsystem and the reference ground.
4 Type Dimensions
The type and dimensions of hexagon flange self-cleaning grounding bolts shall comply with the provisions of Figures 1, 2, and Table 1.
5 Technical Conditions
Technical conditions are specified in Table 2.
Table 2 Technical Conditions
6 Conductivity Test Method
6.1 Test Conditions are specified as follows:
a) Bolts used for testing shall be randomly selected; the number of test samples shall be not less than 25.
b) Unless otherwise specified, testing and measurement shall be conducted at room temperature (20±15)°C and normal humidity (relative humidity (65±20)%).
c) Unless otherwise instructed, connect the grounding terminal and wire on the test steel plate, tighten the bolt with the specified torque, and conduct the test in the locked state, as shown in Figure 3.
d) Requirements for the test steel plate are specified in Table 3.
Table 3 Test Steel Plate Requirements
6.2 Test Connection Requirements are as follows:
a) During bolt tightening, the grounding terminal shall not rotate with the bolt;
b) Use insulating tape to wrap the shank portion of the bolt to insulate it from the test steel plate;
c) The grounding terminal shall have sufficient flat area to ensure bolt installation;
d) Insulation between the grounding terminal and the test steel plate shall be provided using PPC insulating paper.
Note: The surface of the weld nut used for testing shall not be treated, thread tolerance class 6G, other requirements according to QC/T 863.
6.3 Voltage Drop Test Requirements are as follows:
a) Voltage and current range for the controllable discharge battery:
— Voltage: 5V to 12V;
— Discharge current: 100A to 500A (switched every 50A, setting accuracy below 1%).
b) Apply the current specified in Table 4 for 30 seconds to the circuit shown in Figure 4, while simultaneously recording the potential difference between measuring wire A and wire B shown in Figure 3 on an automatic balancing pen recorder, and read the value 30 seconds after energization begins, or measure using a milli-ohm meter.
7 Product Numbering
The product numbering for hexagon flange self-cleaning grounding bolts shall comply with the provisions of QC/T 326.
