STAINLESS STEEL HEXAGON HEAD BI-METAL TEK 3 SCREWS

Hexagon Head Bi-Metal Tek 3 Screws — Step up from Tek 2 and the point geometry changes to handle thicker single-skin steel sections and slightly heavier purlins that would make a Tek 2 point stall or bind rather than drill cleanly. This bare, unwashered hex-head screw is built for fixings that stay inside the building envelope - brackets, cleats, internal structural connections, and stud-to-track or rail-to-purlin joints where no external weather skin is being penetrated - so there's no need for the cost, bulk, or maintenance consideration of a sealing washer. As with every screw in this range, the construction is bi-metal: a stainless steel body and thread carry the corrosion resistance, while a hardened carbon-steel point is brazed to the tip purely to self-drill and self-tap the steel substrate, since a solid stainless point isn't hard enough to do that job reliably at Tek 3 capacity. That's also the reason to reach for this range over a plain stainless self-drilling screw whenever the substrate is genuinely structural steel rather than timber or masonry - plain stainless self-drilling screws exist, but their drilling performance into steel of any real gauge falls well short of a hardened bi-metal point. Selecting the right point rating is mostly about matching drilling capacity to the steel section being fixed into: Tek 2 for light stud and track gauges, Tek 3 for medium-gauge purlins, rails, and structural sections like this one, and Tek 5 where the steel is heavier still or multiple layers need to be cleared. If a Tek 3 point is stalling, generating excess heat, or failing to fully seat rather than drilling through cleanly, that's usually a sign the steel is heavier gauge than this point is rated for, and a Tek 5 screw should be substituted. Length should clear the full thickness of both components being joined plus a small margin of thread engagement in the far side.

FAQs
Is this screw suitable for external, unweathered fixings?
No - it has no sealing washer, so it isn't intended to penetrate an external roof or wall skin; the washered Tek 3 version should be used for any fixing that passes through the weather envelope.

What's a practical sign the steel is too heavy for a Tek 3 point?
Stalling, excessive heat build-up, or the point failing to seat fully rather than drilling through cleanly usually means the section is heavier than Tek 3 is rated for, and a Tek 5 screw should be substituted.

Why choose this over a plain stainless self-drilling screw?
A plain stainless point isn't hardened enough to self-drill medium-gauge structural steel reliably; the bi-metal construction with a brazed carbon-steel point is what makes consistent single-pass drilling possible at Tek 3 capacity.