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Truss Head Self Tapping Screw

Wide Low-Profile Head  ·  Phillips Cross Drive  ·  White Zinc Plated  ·  ST4.2 & ST4.8

The truss head self tapping screw has an extra-wide, low-profile domed head with a cross recessed Phillips drive — significantly larger in diameter than a standard pan head of the same shank size. This wider bearing surface spreads clamping load over a greater area, reducing the risk of the head pulling through thin, soft or brittle material. The fully threaded, self-tapping shank cuts its own thread into a pre-drilled hole in sheet metal, plastic, polycarbonate and wood — no nut or tapping tool required. Excel Trading Corporation stocks this in white zinc plated mild steel.

Specifications

  • Bullet Icon Head Type: Truss head — extra-wide, low-profile dome
  • Bullet Icon Drive: Phillips cross recess (PH)
  • Bullet Icon Thread: Fully threaded, self-tapping — cuts its own thread
  • Bullet Icon Head Dimensions: Head Ø up to 11.5mm, head height 2.6mm
  • Bullet Icon Material: Mild steel, white zinc plated

Applications

  • Bullet Icon Polycarbonate roofing sheets and skylights
  • Bullet Icon Signage, hoardings and display panel fixing
  • Bullet Icon uPVC and PVC cladding panels
  • Bullet Icon Thin gauge sheet metal and fascia boards
  • Bullet Icon Plastic enclosures and lightweight panel assembly
Truss Head Self Tapping Screw

Available In

Steel

White Zinc

Available Sizes — Truss Head Self Tapping Screw

Both sizes are stocked in white zinc plated mild steel. Head diameter is up to 11.5mm with a head height of 2.6mm. Use the pilot hole size below for clean, controlled thread engagement.

Size (ST) Imperial Equivalent Outer Ø (mm) Pilot Hole (mm) Common Lengths
ST 4.2 #8 4.2 3.2 13  ·  16  ·  19  ·  25  ·  32  ·  38 mm (1/2″–1-1/2″)
ST 4.8 #10 4.8 3.7 13  ·  16  ·  19  ·  25  ·  32  ·  38 mm (1/2″–1-1/2″)

Why Choose a Truss Head Over a Pan Head?

The defining feature of a truss head screw is its extra-wide, shallow-domed head profile. Compared to a standard pan head of the same shank diameter, the truss head has a significantly larger outer diameter relative to its height — giving it a much greater bearing surface area. This matters in practice whenever the material being fastened cannot bear a concentrated point load: polycarbonate sheet, signage panels, uPVC cladding, thin gauge sheet metal and fascia boards. The wider head spreads clamping force over more surface area, preventing the head from digging in, cracking, or pulling through the material.

Material & Finish

Mild Steel — White Zinc Plated

Case Hardened · Standard Grade

Case hardened low carbon steel with bright white zinc plating. The hardened thread cuts cleanly through sheet metal, plastic and polycarbonate on the first drive. Zinc plating provides corrosion protection for indoor and sheltered outdoor use. This is the only finish this screw is available in — Excel Trading Corporation does not stock the truss head self tapping screw in stainless steel. For coastal, marine or heavy-corrosion applications, contact us to discuss a stainless steel alternative in a different head style (such as pan head or CSK head).

Best for: Indoor signage · Sheet metal · Plastic & polycarbonate panels · General fabrication

Quick Specifications

ST4.2–4.8

Size Range

11.5mm

Max Head Diameter

Phillips

Drive Type

White Zinc

Finish

Installation Tips

  • ▸ Always drill a pilot hole using the size in the table above — never drive a self tapping screw into undrilled material.
  • ▸ For polycarbonate sheet, drill the pilot hole slightly oversized to allow the panel to expand and contract with temperature without cracking.
  • ▸ Drive at moderate speed — high RPM causes heat build-up in plastic and polycarbonate that can distort the material before the screw fully seats.
  • ▸ Do not overtighten — the wide truss head seats flush when hand-tight. Over-driving can still crack brittle sheet material despite the larger bearing surface.

Frequently Asked Questions

What is a truss head self tapping screw?

A truss head self tapping screw has an extra-wide, low-profile domed head — significantly larger in diameter than a standard pan head for the same shank size. The wide bearing surface spreads clamping load over a larger footprint, reducing the risk of the head pulling through thin or soft material. The self-tapping thread cuts its own thread into a pre-drilled hole, and it uses a Phillips cross drive. Available in ST4.2 and ST4.8.

What is the difference between a truss head and a pan head self tapping screw?

A truss head has a much wider, flatter dome than a pan head of the same diameter — the head bearing surface is significantly larger, so it distributes load over more material. This makes truss head the better choice for thin sheet, polycarbonate, signage panels and other materials where a concentrated load from a narrower pan head could dent, crack or pull through the surface. A pan head is used where a lower head profile is not critical and the material can handle a more concentrated point load.

What pilot hole size do I need?

For ST4.2, drill a 3.2mm pilot hole. For ST4.8, drill a 3.7mm pilot hole. These sizes apply to sheet metal; in softer materials like plastic, polycarbonate or wood, a slightly smaller pilot hole gives better thread engagement. Never drive a self tapping screw into an undrilled hole — it will strip the thread or snap the screw.

Can truss head self tapping screws be used for polycarbonate sheets and signage panels?

Yes — this is one of the primary applications for truss head screws. The wide, low-profile head is specifically suited to polycarbonate roofing sheets, signage and display panels, uPVC cladding and other thin or brittle materials, because the large bearing surface prevents the head from pulling through or cracking the panel. This screw is supplied in white zinc plated finish, suited to indoor and sheltered outdoor use; for coastal or heavy-corrosion environments, contact us to discuss a corrosion-resistant alternative.

Does the truss head self tapping screw come in stainless steel?

No. This product is supplied only in white zinc plated mild steel. If you need a corrosion-resistant fastener for coastal, marine or heavy-moisture environments, contact Excel Trading Corporation — we stock stainless steel options in other self tapping screw head styles such as pan head and CSK head.

Where can I buy truss head self tapping screws in Bangalore?

Excel Trading Corporation stocks truss head self tapping screws in ST4.2 and ST4.8, white zinc plated mild steel, at our Kumbarpet store in Bengaluru. We supply sheet metal fabricators, signage manufacturers and general industry across Karnataka and India-wide. Call +91-9448239476 or email info@exceltrading.in for pricing and availability.