DIN 7504 · Polycarbonate Sheet · Shadow Cove · Steel Framing · Zinc & Stainless Steel
The truss head self drilling screw is a specialised fastener designed for applications where a wide, low-profile head is required. Its extra-large domed bearing surface distributes clamping load over a significantly greater area than a pan head or CSK head — preventing pull-through in thin, soft or brittle materials such as polycarbonate sheet, fibre sheet and shadow cove profiles. Like all self drilling screws, it drills, taps and fastens in a single operation with no pilot hole required. Available in M4.2 and M4.8 diameters, zinc plated and stainless steel finish.
Polycarbonate sheet to steel purlin or metal framing
Shadow cove and fibre sheet to steel secondary structure
Residential light gauge steel frame construction
Brick ties and accessories to steel framing
HVAC duct and insulation panel to metal substrate
Light gauge metal-to-metal fastening in general fabrication
Extra-wide low-profile dome head — large bearing area prevents pull-through
Phillips drive — self-centering, takes more torque without cam-out
Non-walking drill point — fast material engagement, no pilot hole needed
Drills, taps and fastens in one single operation
Zinc plated for corrosion resistance — stainless steel for outdoor and coastal use
Heat treated carbon steel for hardness, torsional strength and drill performance
White Zinc
Stainless Steel
| Size | Length (inch) | Length (mm) | Drill Point (m/m) | Drill Capacity (m/m) |
|---|---|---|---|---|
| #8-18 M4.2 | 1/2” | 13 | #2 | 1.0 - 2.0 |
| 5/8" | 16 | #2 | 1.0 - 2.0 | |
| 3/4" | 19 | #2 | 1.0 - 2.0 | |
| 1" | 25 | #2 | 1.0 - 2.0 | |
| 1" | 50 | #3 | 2.0 - 4.0 | |
| 1-1/4" | 32 | #2 | 1.0 - 2.0 | |
| 1-1/2" | 38 | #2 | 1.0 - 2.0 | |
| #10-16 M4.8 | 1/2” | 13 | #2 | 1.0 - 2.0 |
| 5/8” | 16 | #2 | 1.0 - 2.0 | |
| 3/4" | 19 | #2 | 1.0 - 2.0 | |
| 1" | 25 | #3 | 1.0 - 3.0 | |
| 1-1/4" | 32 | #3 | 1.0 - 3.0 | |
| 1-1/2" | 38 | #3 | 1.0 - 2.0 | |
| 2" | 50 | #3 | 1.0 - 3.0 |
The defining feature of a truss head screw is its extra-wide, shallow-domed head profile. Compared to a standard pan head, the truss head has a significantly larger outer diameter relative to its height — giving it a much greater bearing surface area. This is not a cosmetic difference. In practical terms, the wider head distributes the clamping force across a larger footprint, which is critical when fastening into materials that cannot bear concentrated point loads — polycarbonate sheet, fibre cement board, shadow cove, thin aluminium and light gauge steel.
In applications where a standard pan head screw would pull through the sheet under load or vibration, the truss head holds. This is why it is the specified fastener type for polycarbonate roofing and cladding sheets across India.
Extra-wide shallow dome. Largest bearing area of any self drilling screw head type. Best choice for polycarbonate, fibre sheet and thin soft materials. Low profile above the surface.
Standard dome, narrower than truss. Used for general metal-to-metal fastening. Higher profile above the surface. Not suitable for pull-through sensitive materials.
Countersunk flat head — sits flush with the surface. No bearing area above the surface. Used for drywall, timber and applications where a flush finish is required.
Polycarbonate sheets expand and contract significantly with temperature changes — a critical factor in India where daily temperature swings are large and sun exposure is intense. When fastening polycarbonate sheet to a steel substrate, the truss head self drilling screw should always be used with a neoprene or EPDM washer to seal the fastening point and prevent water ingress. The clearance hole in the polycarbonate sheet should be slightly oversized relative to the screw shank — this allows the sheet to move with thermal expansion without cracking around the fastening point.
The M4.2 (#8-18) size is the standard choice for polycarbonate sheet to light gauge steel framing. The Drill Point #2 on the M4.2 penetrates up to 2.0mm steel cleanly without the need for a pilot hole. For thicker steel substrates, the M4.8 (#10-16) with Drill Point #3 handles up to 4.0mm steel.
Installation note
Do not overtighten truss head screws into polycarbonate. Drive until the washer just compresses — over-tightening cracks the sheet around the fastening point and voids the panel. Use a torque-limited driver where possible.
In residential and commercial interiors, truss head self drilling screws are widely used for shadow cove profiles — the recessed ceiling line detail used in modern construction. The wide head sits flat against the face of the shadow cove aluminium or steel extrusion without marking or damaging the surface finish, while the low profile above the surface keeps the detail clean.
In light gauge steel frame construction — residential walls, partitions, ceiling grids and HVAC duct runs — the truss head screw provides fast, reliable fastening of accessories, brackets and secondary elements to the primary steel framing without pilot holes. The M4.2 size covers most light framing applications from 13mm to 38mm length.
| Drill Point | Steel Penetration | Screw Size | Typical Application |
|---|---|---|---|
| Point #2 | 1.0mm – 2.0mm | M4.2 (most lengths) | Polycarbonate / shadow cove / light steel framing |
| Point #3 | 1.0mm – 4.0mm | M4.8 / M4.2 (2" length) | Heavier steel framing / thicker substrates |
A truss head self drilling screw has an extra-wide, low-profile domed head that distributes clamping load over a larger bearing area than a pan or CSK head. It drills, taps and fastens in a single operation with no pilot hole. Preferred for polycarbonate sheet, fibre sheet, shadow cove and light gauge steel frame applications.
Yes — the truss head is the preferred choice for polycarbonate sheet. The large bearing area prevents the head from pulling through. Always use with a neoprene or EPDM washer for outdoor applications, and use slightly oversized clearance holes to allow for thermal expansion of the sheet.
A truss head has a wider, flatter dome with a much larger bearing surface diameter than a pan head. This makes it better for thin or soft materials where pull-through is a risk. A pan head has a taller, narrower profile and is used for standard metal-to-metal fastening.
We stock M4.2 (#8-18) in lengths 13mm to 38mm and M4.8 (#10-16) in lengths 13mm to 50mm. Zinc plated and stainless steel. Call +91-9448239476 for bulk pricing and availability.
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