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Electrogalvanized cross countersunk drill thread
The head is a cross-groove countersunk design, which can be hidden in the installation surface to keep the surface flat. The drill bit diameter matches the thread diameter (such as ST4.2 drill bit diameter 4.2mm), which complies with GB/T 15856.1-2002 standard.
Description
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Product Introduction
Structural features: The head is a cross-groove countersunk design, which can be hidden in the installation surface to keep the surface flat. The drill bit diameter matches the thread diameter (such as ST4.2 drill bit diameter 4.2mm), which complies with GB/T 15856.1-2002 standard.
Performance parameters: surface hardness HV580-720, core hardness HV350-420, salt spray test 24-48 hours. The maximum tensile load of M4 specification in aluminum plate is about 8kN.
Application scenarios: ceiling keel fixing in building decoration, furniture manufacturing, electronic equipment housing assembly, etc., suitable for scenes with high requirements for aesthetics.
Key comparison and selection recommendations
| Type | Surface treatment | Salt spray test | Hardness range | Corrosion resistance | Environmental protection | Typical application scenarios |
| Electro-galvanized hexagonal head | Silvery white | 24-48 hours | HV560-750 | General | No hexavalent chromium | Indoor steel structure, ordinary mechanical connection |
| Colored zinc-plated hexagonal head | Rainbow color | More than 72 hours | HV580-720 3 | Good | Trivalent chromium environmental protection | Outdoor photovoltaic bracket, port equipment |
| Black zinc-plated hexagonal head | Black | More than 96 hours | HV600-700 | Excellent | Trivalent chromium environmental protection | Automobile chassis, high-temperature equipment |
| Electro-galvanized cross countersunk head | Silvery white | 24-48 hours | HV580-720 | General | No hexavalent chromium Indoor decoration, furniture manufacturing | Colored zinc-plated cross countersunk head |
| Rainbow color | More than | 72 hours | HV580-720 | Good | Trivalent chromium environmental protection | Outdoor awnings, bathroom equipment |
Selection suggestions:
Environmental factors: For outdoor or high humidity environments, color zinc plating or black zinc plating is preferred; for indoor dry environments, electroplating zinc can be selected.
Load requirements: For high-load scenarios (such as bridges and heavy machinery), black zinc-plated hexagonal drill tail screws must be selected. Specifications above M8 must be tested for torque according to GB/T 3098.11.
Environmental requirements: Electroplating zinc (chromium-free) is recommended for the medical and food industries; trivalent chromium passivated color zinc plating or black zinc plating can be selected for ordinary industrial projects.
Installation specifications:
Electric drill speed control: 3.5mm diameter drill tail screws are recommended to be 1800-2500 rpm, and 5.5mm diameter drill tail screws are recommended to be 1000-1800 rpm.
Torque control: The torque of the M4 specification is about 24-28kg・cm, and the M6 specification is about 61-70kg・cm. Avoid deformation of the substrate due to excessive tightening.
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