Full Mechanical Test Specification For S/CLS Press Nuts, SO/BSO Studs & FHS Press Screws, Based On GB/T17880 & JB/T8465 Thin Sheet Riveting Standard

Full Mechanical Test Specification For S/CLS Press Nuts, SO/BSO Studs & FHS Press Screws, Based On GB/T17880 & JB/T8465 Thin Sheet Riveting Standard

Precision press-fit fasteners are core embedded fasteners for 1.0-3.0mm thin sheet metal, widely used in TWS earbuds, notebooks, energy storage electrical control cabinets and communication server chassis. Mechanical locking is formed by cold plastic deformation of sheet metal, pull-out and anti-torsion performance directly determine vibration reliability of complete equipment. All test loads, sampling rules and failure judgment standards in this article are from special national standards for thin sheet press-fit parts and acceptance standards of top electronic manufacturers, exclusively covering press-fit products without overlapping craft content of construction bolts and import lock fasteners, complete three-stage inspection process of incoming material, press-fit assembly and finished delivery.

1. Standard Minimum Pull-out Force & Anti-torsion Torque For Mainstream M3-M6 Press-fit Parts (Specified By GB/T17880)

2. Four-stage Standardized Delivery Inspection Process For Press-fit Parts (First Article-Patrol-Assembly Verification-Final)

1. Incoming Raw Material Inspection: Spectrum material screening for stainless press-fit parts to block inferior grade 201 stainless steel; coating thickness test for carbon steel parts, electro-galvanized 5-8μm, Dacromet ≥8μm, rejected if below standard. 2. Finished Mechanical Sampling (AQL0.65 per batch): Randomly extract 50pcs for dual pull-out & anti-torsion test, whole batch unqualified if value below national standard minimum in table, re-test after adjusting press mold. 3. Sheet Metal Assembly Verification Test: Match standard sheet of corresponding thickness, press with servo press at standard pressure, check no bulging on sheet back and fully flush front surface; bulging means excessive press pressure or insufficient sheet thickness. 4. Anti-corrosion Durability Sampling: Add 48h NSS salt spray test for stainless press-fit parts supporting outdoor cabinets, qualified without white rust or coating peeling before delivery to energy storage & security clients.

3. Four High-frequency Press-fit Failure Objective Causes (Sheet Metal Factory Defect Statistics 2026)

1. Sheet back bulging after pressing: Excessive press pressure parameter setting, sheet thickness lower than product matching limit; rectify: reduce press pressure by 10%, replace sheet of matching thickness or select larger flange press model. 2. Insufficient pull-out force & direct pull-out under load: Oversize pre-drilled hole, insufficient press-in stroke, insufficient metal flange engagement volume; rectify: strictly control hole tolerance 0~+0.075mm, extend equipment pressure holding time to 0.5s. 3. Press-fit part torsion slip during screw tightening: Offset mold coaxiality, excessive sheet hardness, rolling grain cannot form effective lock; rectify: calibrate press head coaxiality, anneal cold rolled plate with excessive hardness. 4. Thread stripping after repeated disassembly: Burrs on thread rolling process, out-of-tolerance pitch diameter; rectify: optimize thread rolling mold, add ultrasonic deburring process for finished goods, full thread inspection for precision electronic parts.

4. Mandatory Acceptance Red Line For Press-fit Parts Purchased By 3C & Energy Storage Cabinet Manufacturers (Unified Standard Of Top Electronic Equipment Factories)

First, S micro flange press nuts must be adopted for ultra-thin sheet below 1.0mm, conventional large flange models prohibited to avoid back protrusion interfering internal electronic components; Second, SUS304 FHS stainless press screws for all outdoor energy storage equipment, ordinary electro-galvanized carbon steel versions not purchased to prevent condensation corrosion; Third, complete pull-out & anti-torsion mechanical test summary report attached to each batch, goods rejected without report before assembly; Fourth, add 500,000-cycle alternating vibration pre-test for press-fit parts used in vibration equipment, minimum 80% residual pull-out force retention rate required for mass production.