What are the testing standard for self-tapping insert ?

Before shipment, self-tapping  inserts must undergo the following inspections according to national standards and industry practices. Only those that pass the inspections can be released:

1. Appearance and Dimensions

– Threads must be intact, without defects or burrs; the head and tail must be free of deformation; the surface must be smooth, free of rust and scratches.

– Use caliper gauges, ring gauges, and plug gauges to randomly inspect the main dimensions (outer diameter, length, pitch, thread angle). Tolerances must conform to the drawings or GB/T 196/197 requirements.

2. Hardness and Carburized Layer

– Surface hardness: Martensitic steel ≥300 HV; core hardness controlled according to material grade (20H/25H, etc.).

– Carburized layer depth: According to GB/T 3098.7, three samples should be taken from the same batch, and the measured value should be between the upper and lower limits of the process documents.

3. Breaking Torque

– Apply torque slowly on a dedicated fixture until fracture, and record the breaking torque value; it must be ≥ the minimum value given in Table 5 of standard GB/T 3098.21 (e.g., ST4.2-30H not less than 3.9 N·m).

4. Screw-in Performance

– Screw the insert into a test plate of aluminum alloy (80-120 HV) or low carbon steel (130-170 HV) of specified thickness and hole diameter until one complete thread emerges; the thread must not be stripped or chipped, and the screwing torque should be smooth and without jamming.

5. Tensile/Torsion Retention Force (for self-tapping steel inserts)

– After installation onto a standard aluminum test block, apply the specified preload with a torque wrench; the insert should not rotate circumferentially; continue applying pull-out force, and it is considered合格 (qualified) if it does not pull out when the design value is reached.

6. Coating and Corrosion Protection (if applicable)

– Coating thickness shall be tested according to GB/T 5267.1; neutral salt spray test ≥ 48 h with no red rust; adhesion shall meet the “Cross-cut Grade 1” requirement.

7. Packaging and Labeling

– According to GB/T 90.2: The inner bag shall include a certificate of conformity (including batch number, material, specifications, and quantity); the outer box shall be affixed with moisture-proof and shock-proof labels, and accompanied by a shipping inspection report.

The above items are routine mandatory inspection contents; if the customer has special requirements (such as vibration life, torque attenuation, RoHS, DFAR), corresponding tests can be added and included in the quality agreement.