Product Summary

Longze DIN 7981 Phillips Pan Head Self-Tapping Screws (equivalent to ISO 7049) are engineered for high-torque fastening into sheet metal, aluminum, and plastics without

the need for pre-tapping. Manufactured in Yongnian, China, our self-tapping screws feature precision-formed Type AB or Type B threads and deep-seated Phillips drives to prevent

driver slippage. Whether for HVAC ductwork or electronic enclosures, Longze screws provide the sharp penetration and superior holding power required for high-speed assembly.

• ✔ Precision Phillips Drive: Deep, standardized #1, #2, and #3 Phillips recesses prevent "cam-out," extending tool life and reducing assembly damage.

•  

• ✔ Hardened Thread Crests: Case-hardened carbon steel ensures the threads can cut their own mating threads in cold-rolled steel up to 3mm thick.

•  

• ✔ Low-Profile Pan Head: The rounded top and flat bearing surface provide a clean, professional finish while distributing clamping pressure evenly.

• Standards: DIN 7981, ISO 7049, ANSI/ASME B18.6.3.

•  

• Diameter Range: ST2.2 to ST6.3 (#2 to #14).

•  

• Length Range: 6.5mm to 100mm (1/4" to 4").

•  

• Material Grade: Case-Hardened Carbon Steel (C1022A) | Stainless Steel 304 (A2) & 316 (A4).

•  

• Surface Finish: Zinc Plated (Blue/White/Yellow), Black Oxide, Nickel Plated, Ruspert.

Mechanical Properties & Material Standards

• Matching the steel grade to the structural requirements of the transmission line.

• Material Grade	Surface Hardness	Core Hardness	Tensile Strength	Recommended Substrate
  C1022A (Steel)	≥ 450 HV	270 - 390 HV	600 - 800 MPa	Sheet Metal / Ducting
  SS304 (A2)	N/A	200 - 280 HV	500 - 700 MPa	Food / Outdoor PVC
  SS316 (A4)	N/A	240 - 320 HV	800 MPa	Marine / Chemical

Standard Cross Arm Dimensions

• Common angle steel configurations for standard utility pole mounting.

• Thread Size (ST)	Head Dia (dk)	Head Height (k)	Driver Size (PH)	Drilling Capacity
  ST3.5 (#6)	6.9 mm	2.6 mm	PH2	≤ 1.5 mm Steel
  ST4.2 (#8)	8.2 mm	3.05 mm	PH2	≤ 2.1 mm Steel
  ST4.8 (#10)	9.5 mm	3.55 mm	PH2	≤ 2.5 mm Steel
  ST5.5 (#12)	10.8 mm	3.95 mm	PH3	≤ 3.0 mm Steel

Galvanizing & Corrosion Resistance

• Ensuring 30+ years of service life in corrosive environments.

• Surface Treatment	Process	Salt Spray Test	Service Life	Application
  Zinc Plated	Electrolytic	24 - 72 Hours	High	Indoor Appliances
  Black Oxide	Chemical	12 - 24 Hours	Moderate	Interior Electronics
  Ruspert (Silver)	Multi-Layer	500 - 1000 Hours	Maximum	Outdoor Window/Door

Avoid Pitfalls:

• Head Snapping (Hydrogen Embrittlement): For hardened carbon steel screws, we perform a 4-8 hour de-embrittlement bake after plating to prevent heads from snapping off days after installation.

•  

• Shallow Phillips Recess: We monitor our heading dies every 50,000 pieces to ensure the Phillips drive is deep enough. A shallow drive leads to "stripping," which is the #1 complaint in high-speed production lines.

•  

• Stainless Steel Galling: When using SS304/SS316 screws in stainless sheet metal, we recommend using a lower RPM driver or a specialized lubricant to prevent thread seizing (galling).

•  

Perfect Fit Assembly:

• Pre-Drill Guidance: For maximum grip, we provide recommended pilot hole charts based on the thickness and hardness of your base material (Steel vs. Aluminum vs. Plastic).

•  

• Nylon Washer Integration: We can supply DIN 7981 screws with Pre-Assembled EPDM or Nylon Washers for applications requiring a watertight seal or vibration dampening.

•  

Quality Control & Logistics:

• ISO 9001 Certified: 5-step QC including drilling speed tests, torque-to-fail verification, and thread pitch gauge inspection.

•  

• Sea-Worthy Packaging: Standard export packaging includes 1,000pcs per inner box or bulk 25kg cartons, plastic-lined and palletized for zero-moisture transport.

• Q: What is the difference between Type AB and Type B threads? A: Type AB has a pointed tip for easier entry into thin sheet metal, while Type B has a blunt tip for use in pre-drilled holes or plastics. We supply both based on your application.

• Q: Why are my stainless steel self-tapping screws magnetic? A: High-speed cold heading slightly alters the microstructure of 304/316 steel, introducing "work-induced magnetism." This is normal and does not affect the corrosion resistance of the material.