STAINLESS STEEL PHILLIPS COUNTERSUNK BI-METAL WING DRILL TIMBER TEK 3 SCREWS

Phillips Countersunk Bi-Metal Wing Drill Timber Tek 3 Screws — Fixing timber straight through into steel in one pass sounds simple until the timber itself gets in the way - a standard self-drilling point can grip and bind in dense or treated timber before it ever reaches the steel beneath, building up heat and stalling rather than drilling cleanly. The wings moulded into this screw's point solve that: they ream a clearance hole through the timber layer ahead of the thread, then shear off cleanly the moment they contact the steel substrate, leaving the Tek 3 point to self-drill into the steel without the timber fighting it. That makes this the right choice wherever timber battens, boards, or sub-structure need fixing directly to a steel purlin or rail in a single operation - cladding support systems, timber cill rails on steel-framed buildings, and similar composite timber-over-steel details, rather than fixing timber to timber or timber to masonry, where a standard woodscrew or Tek-free fixing is more appropriate. Bi-metal construction underpins the whole design: a stainless body and thread resist the weathering and treated-timber chemical exposure this kind of external fixing sees, while the hardened carbon-steel point, wings included, does the mechanical work of clearing timber and then drilling steel that a solid stainless point couldn't manage. Tek 3 point rating matches this screw to medium-gauge purlins and structural sections once the wings have done their job; where the steel behind the timber is a heavier section, the Tek 5 wing-drill version should be specified instead of pushing a Tek 3 point beyond what it can clear. Getting length right is more critical here than on a standard Tek screw, since it needs to clear the full timber thickness, allow the wings to shear at the correct point, and still achieve solid engagement in the steel beyond - too short and the point never reaches solid steel; too long and there's excess unused thread.

FAQs
What happens if the wings don't fully shear off?
They're designed to shear cleanly on contact with the steel substrate; a poor result usually points to incorrect screw length or the timber layer being thicker than expected, which is why matching length to the actual timber-and-steel build-up matters.

Can this be used for timber-to-timber fixing instead?
Not ideally - if there's no steel substrate to drill into, a standard woodscrew or timber fixing is more suitable, since the wing-and-point combination is specifically engineered around clearing timber before drilling steel.

How does this compare with the Hexalobular Wing Drill Tek 3 version?
Both share the identical wing-drill point and Tek 3 steel capacity; the difference is drive type, with hexalobular offering better cam-out resistance under high torque and Phillips being a more universally available bit.