Product Overview
Double thread hex washer head self-drilling screws are engineered for fastening metal roofing sheets and steel components where both structural holding strength and weather sealing are required. The integrated EPDM bonded washer forms a durable compression seal that prevents water penetration while maintaining long-term elasticity under outdoor conditions.
The dual-thread design improves driving efficiency and provides enhanced pull-out resistance compared with conventional single-thread screws, making it suitable for industrial roofing, steel frame assembly and panel installation.
ASME IFI and Metric standard Size
|
Diameter |
Length |
|
#6-20(ST3.5) |
1/2''-2''inch (13-50mm) |
|
#8-18(ST4.2) |
1/2''-2''inch (13-50mm) |
|
#10-16(ST4.8) |
1/2''-4''inch(13-100mm) |
|
#12-14(ST5.5) |
1/2''-6''inch(13-150mm) |
|
#14-14(ST6.3) |
1/2''-6''inch(13-150mm) |
| Material | Carbon C1022 Steel, Case Harden&Stainless Steel |
| Head Type | hex washer head |
| Thread Type | full thread, partial thread |
| Surface Finish | Black/grey phosphate, White/yellow zinc plated ,Nickel,Ruspert. |
| Diameter | #8 (4.2mm), #10 (4.8mm), #12 (5.5mm), #14 (6.3mm) |
| Point | Drilling Tail |
| Standard | Din 7504K |
| Non-standard | OEM is available if you provide drawings or samples. |
| Packing | box, bulk in carton or bags ,polybag or Customer request |
Key Features
Double Thread Design
Double thread (dual pitch) design for enhanced holding strength
01
Suitable for High-Efficiency Assembly Lines
Bonded EPDM washer for waterproof sealing
Optimized thread geometry to reduce installation torque
02
Self-Drilling Tip
Self drilling Tek point for fast penetration into steel
Hex washer head for high torque transmission
03
Anti-Vibration Grip
Double threads reduce loosening under load.
04
Durable Coatings
High-strength carbon steel or stainless steel material
Excellent corrosion resistance with advanced coating
05
Common Applications
Double thread hex head self drilling screws with EPDM washer are widely used in:
Metal roofing systems
Steel structure construction
Purlin and sheet metal fixing
Sandwich panel installation
Solar mounting systems
Industrial and commercial buildings
Metal-to-metal fastening
Advantages of Double Thread Design
Compared with standard single-thread self drilling screws, double thread screws offer:
Higher pull-out resistance
Better vibration resistance
Faster installation speed
Improved load distribution
Stronger clamping force
Installation Tips
- Use an impact driver or drill with a hex socket bit.
- Drive at medium speed to protect the drill point.
- Select a length that allows the drill tip to fully penetrate steel.
- Stop once the washer is snug; overtightening can damage coatings.
The double thread hex washer head self-drilling screw is a high-performance fastener built for speed, strength, and reliability. With its self-drilling tip, strong hex washer head, and unique double-thread design, it offers faster installation, superior grip, and long-lasting hold in construction and steel applications.
Design Features That Make a Difference
Double-Lead Threading for Efficient Progress
The "double thread" (also called dual-lead or twin thread) configuration features two thread starts on the screw body. This results in:
Faster thread engagement - each rotation drives the screw further than a single-lead thread
Reduced drive time - improves productivity on repetitive installations
Improved thread holding power in both thin and medium gauge materials
For installers covering large surface areas or high-volume fastening tasks, this means less time per fastener and smoother workflow overall.
Compared with standard self-drilling screws, the double-thread structure offers improved installation performance in steel substrates. The screw engages the material more efficiently, reducing driving time while maintaining strong mechanical retention. The bonded sealing washer maintains consistent compression, helping to protect the joint from moisture ingress and environmental exposure.
Hex Washer Head – Wider Bearing Surface
The integrated hex washer head adds value by:
Providing a broader contact area for better load distribution
Enhancing torque transfer from driver bits
Reducing surface indentation or material distortion
Supporting faster seating during drive-in
This head style works especially well with power drivers and impact tools, helping maintain consistent installs even under demanding job site conditions.
Comparison Table
| Feature | Double Thread SDS Screw | Single Thread SDS Screw |
|---|---|---|
| Holding strength | High | Medium |
| Installation speed | Fast | Normal |
| Vibration resistance | Excellent | Average |
| Roofing suitability | Ideal | Standard |
Real-World Uses & Suitable Projects
These screws are commonly chosen for a wide range of applications, including:
Roofing and facade systems
Metal building assemblies
Light structural framing
Equipment anchors and brackets
Prefabricated panel installations
Mechanical enclosures and housings
In every case, the dual-thread design helps deliver consistent penetration and secure grip while maximizing installation speed.
Material & Coating Options (Why They Matter)
To suit different environments and performance needs, these screws are available with multiple material and finish options:
Material Types
Carbon steel: Standard strength with solid cost-performance
Stainless steel: Enhanced corrosion resistance for harsh or humid environments
Surface Finishes
Zinc plating: Basic protection against oxidation
Hot dip galvanized: Stronger corrosion resistance for outdoor exposure
Color-coated finishes: Aesthetic alignment with panel surfaces
Choosing the right finish helps ensure long-term durability in your specific environmental conditions.
Installation Best Practices
To maximize performance and service life:
Select correct screw length - ensure full thread engagement without overshoot.
Use compatible driver bits - avoid stripping the hex washer head.
Apply consistent torque - over-tightening can stress materials.
Ensure panel alignment - improves thread engagement and sealing where needed.
Following these tips helps reduce rework and supports stronger, more reliable joints.
FAQ
Q1: What is a double thread self drilling screw?
A double thread self drilling screw features two different thread profiles or pitches, designed to improve fastening strength and stability in metal roofing applications.
Q2: Why are double thread screws used in roofing?
They provide better holding power and reduce loosening caused by vibration, wind load, and thermal expansion.
Q3: Are double thread screws suitable for steel structures?
Yes, they are widely used in steel-to-steel fastening and roofing systems.
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