Navien Screw Truss Head Taptite M4 x 10 STS410 20019083A

A truss head Taptite screw, M4 x 10, manufactured in STS410 and supplied by Navien for its NCB-CE, NCB300 and NCB500 boiler ranges. Taptite thread-forming geometry cuts its own mating thread in the parent material, so it is used where a fixing point is formed in sheet metal or cast componentry rather than in a pre-tapped hole. The truss head spreads clamping load over a wider area than a pan or countersunk head, which suits securing panels, brackets and internal assemblies.

• The screw is missing from its fixing point after a service or panel removal.
• The head is rounded or chewed, so the screw can no longer be driven or removed cleanly.
• The thread has stripped in the parent material and the screw will not hold torque.
• Corrosion or surface pitting on the head or shank.
• A panel, bracket or internal component is loose and rattling because the fixing is not clamping.

• Confirm the appliance model and serial number against the fitment list above.
• Check the fixing point takes an M4 x 10 truss head Taptite screw and not a different thread size or head type.
• Inspect the parent thread — if it has stripped, a same-size screw will not restore the fixing.
• Count how many fixings are required before ordering.