The ULAMEX EJ Self-Drilling Screw is a compact, high-strength fastener manufactured entirely from A2 stainless steel (1.4301 / AISI 304), designed for connecting thin-gauge steel components in photovoltaic mounting assemblies. At 5.5×25 mm, it provides self-drilling capability for steel-to-steel connections without pre-drilling — ideal for trapezoidal sheet clamp attachment, carport structural joints, and cable management accessory mounting.
Technical Specifications
| Parameter | Value |
|---|---|
| Material | A2 stainless steel (1.4301 / AISI 304) |
| Size | 5.5×25 mm |
| Drive | Hexagon head |
| Point type | Self-drilling (drill point) |
| Thread | Self-tapping for thin-gauge steel |
| Drilling capacity | Steel sheet 0.5–1.2 mm (combined) |
| Spanner size | 8 mm hex |
Installation Guidelines
Align the components to be joined, ensuring the drill point contacts the steel surface squarely. Using a power drill or cordless driver with an 8 mm hex socket bit, apply steady pressure at moderate speed (300–500 RPM). The self-drilling point cuts its own hole through the thin-gauge steel, and the self-tapping thread immediately engages to form a secure metal-to-metal connection.
The compact 5.5 mm diameter makes this screw suitable for connections where larger fasteners would be impractical or excessive — such as attaching cable management brackets, small mounting plates, or reinforcement gussets to steel profiles. Do not over-tighten: once the screw head seats firmly against the component surface, additional torque risks stripping the self-tapped thread in thin material.
For connections bearing structural loads, ensure the total combined thickness of the steel components does not exceed the screw’s drilling capacity (1.2 mm combined). For thicker materials or structural connections, use bi-metal self-drilling screws (ULAMEX product 445) or pre-drill and bolt with DIN 933 hex bolts.
Applications
- Trapezoidal sheet clamp fixings — attaching PV rail clamp bases to trapezoidal sheet metal roofing
- Carport mounting systems — steel-to-steel connections in PV carport and canopy structures
- Cable management — securing cable trays, conduit clamps, and cable ties to steel mounting frames
- Accessory mounting — attaching small brackets, gussets, and stiffeners to thin-gauge steel profiles
- Ground-mount substructures — secondary connections in ground-mount steel post systems
Material Properties
Unlike bi-metal self-drilling screws that combine two materials, the EJ screw is manufactured entirely from A2 stainless steel. This provides uniform corrosion resistance along the entire fastener length — there is no dissimilar metal junction that could become a corrosion initiation point. The trade-off is somewhat lower drilling capacity compared to bi-metal screws: the A2 drill point is effective for thin-gauge steel (up to ~1.2 mm combined) but does not match the penetration power of a hardened carbon steel tip.
A2 stainless (1.4301) maintains its mechanical properties across the full PV operating temperature range and provides atmospheric corrosion resistance without supplementary coatings, ensuring reliable performance over the system’s 25+ year lifespan.
Compatibility
The ULAMEX EJ self-drilling screw is used with:
- Trapezoidal sheet clamps — thin-gauge steel mounting brackets for metal roof PV systems
- PV profiles — accessory attachment to steel mounting substructures
- Cable clips and conduit clamps — steel cable management components
- Carport and ground-mount steel structures — secondary and non-structural connections
Why ULAMEX
ULAMEX is an EN 1090 certified B2B wholesaler for complete PV mounting systems. EJ self-drilling screws are stocked alongside profiles, clamps, and the full range of PV fastening hardware. Bulk packaging available with pallet delivery across Europe.
Frequently Asked Questions
Q: What is the difference between EJ screws and bi-metal self-drilling screws?
EJ screws are made entirely from A2 stainless steel — suitable for thin-gauge steel up to ~1.2 mm. Bi-metal screws have a hardened carbon steel drill tip that penetrates thicker steel (up to 1.5 mm). Choose EJ for thin material and uniform corrosion resistance; choose bi-metal for thicker sheet penetration.
Q: Can EJ screws replace bi-metal screws for trapezoidal roof mounting?
For standard trapezoidal sheet (0.5–0.75 mm), EJ screws are adequate. For thicker profiles (0.88–1.25 mm) or structural connections, bi-metal screws provide more reliable drilling performance and higher pull-out strength.
Q: Do EJ screws need EPDM washers?
EJ screws do not come with pre-assembled EPDM washers. If the screw penetrates a roof surface where waterproofing is needed, add a separate EPDM bonded washer. For internal steel-to-steel connections (not roof-penetrating), no washer is required.
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