China Phillips Combination Screw Supplier & Factory

A Phillips combination screw (commonly designated as a SEMS fastener) is cold-headed with an unthreaded shank over which one or multiple washers are automatically placed before the thread-rolling operation. As the external thread is rolled, its major diameter expands past the inner diameter of the washer hole, permanently retaining the washer on the shank while permitting free rotation. This eliminates human errors such as forgotten or incorrectly oriented washers, optimizes inventory line items, and accelerates automated vibratory-bowl feeder assembly speeds.

Carbon and alloy steel fasteners with core hardness exceeding 320 HV (approx. 32 HRC), such as Class 8.8, 10.9, and case-hardened thread-rolling screws, are vulnerable to atomic hydrogen pickup during acid pickling and electrolytic zinc electroplating. We follow strict de-embrittlement protocols in line with ISO 4042. Screws are transferred to controlled baking ovens within 1 to 4 hours post-plating, maintaining a temperature of 200°C to 230°C for a continuous duration of 8 to 24 hours (depending on geometry and strength class) to thoroughly diffuse hydrogen out of the steel microstructure.

Yes. We manufacture hybrid combination screws with multi-washer stacks or custom-stamped geometries. For example, a common design integrates an internal-tooth lock washer below a wide flat brass or copper washer to penetrate non-conductive powder coatings on sheet metal panels, establishing reliable electrical ground paths. Alternatively, combination screws can be combined with bonded EPDM or integrated under-head fluoroelastomer O-rings to deliver simultaneous mechanical clamping and IP67/IP68 ingress protection against dust and moisture.

For standard catalogue dimensions (M2 to M10), our minimum production run is typically 50,000 units. For bespoke OEM drawings requiring custom tooling punches, header dies, or specialized washer dies, initial prototype sampling takes 10 to 14 working days, with mass manufacturing lead times spanning 3 to 4 weeks. Full PPAP documentation (Control Plan, PFMEA, Dimensional Results, Material Certifications) is provided to ensure rapid sign-off for automotive and tier-one OEM programs.

To resist dynamic vibratory loosening, we offer three main approaches: (1) SEMS assemblies with conical Belleville or helical split spring washers to maintain continuous axial preload; (2) Pre-applied microencapsulated chemical threadlockers (such as Dri-Loc or precote) that cure upon engagement; and (3) 180° or 360° blue/yellow polyamide (nylon) patches permanently fused to the male threads. The nylon patch produces prevailing torque through radial interference, allowing repeated adjustments without degrading joint clamp load.