Bi-Metal Hex Washer Head Self-Drilling Screw

Overview

Our most specified bi-metal screw. The stainless body sits in the weather; the hardened SS420 tip drills through steel up to 6 mm and ends up inside the purlin, away from rain.

Single or double thread, 25–300 mm long, with stainless steel-backed EPDM washers in grey or black.

Applications

Coastal and industrial roofing
Solar mounting
Chemical plants

Used in these projects

Rooftop solar on trapezoidal metal roofs

Key features

Stainless where it is exposed, hardened where it drills
Drills up to 6 mm steel
Stainless-backed EPDM washer
CE, BV and ISO documentation

Specifications

Typical values. Every dimension, hardness and coating is confirmed in writing with your quotation.

Bi-Metal Hex Washer Head Self-Drilling Screw specifications
Body	SS304 or SS316
Tip	SS420, hardened
Diameter	M4.8, M5.5, M6.3, M7
Length	25–300 mm
Point	#1, #3, #5
Washer	SS304/316 + EPDM, grey or black
Finish	Plain or ceramic coated
MOQ	10,000 pcs
HS code	7318.14 / 7318.12 (by type)

Buying guide

Applies to all bi-metal screws.

304 or 316 body

A2 (304) suits inland exterior use. A4 (316) contains 2–3 % molybdenum and resists chloride pitting, so specify it within about 5 km of the sea, near pools or in chemical plants.

Tip material

SS410/SS420 tips keep some corrosion resistance; SCM435 and C1022 tips drill faster in thick steel. The tip should break through before the stainless threads engage.

Isolate dissimilar metals

On aluminium solar rails and cladding use a stainless EPDM washer or a coated screw to reduce galvanic corrosion between the fastener and the profile.

Ordering

Packing and delivery

Standard terms for this product. Tell us if your market needs something different.

PackingSmall boxes, buckets or 20–25 kg cartons on fumigated pallets; private label available.

Lead timeSamples in 7 days; production 25–35 days after deposit.

PaymentT/T 30 % deposit, 70 % against B/L copy, or L/C at sight.

ShippingFOB Shanghai or Ningbo, CFR or CIF to your port.

Questions about this product

How thick a steel section can a bi-metal screw drill?

Depending on point size, from 0.75 mm sheet up to about 6 mm structural steel. For thicker purlins we recommend a #5 point carbon screw or pre-drilling.

Are bi-metal screws magnetic?

The 304/316 body is mostly non-magnetic, while the hardened tip is magnetic. That is a quick way to confirm a bi-metal screw on site.

Do you supply mill certificates?

Yes. Each lot ships with a material test certificate covering chemistry, hardness, case depth and salt spray results.

Bi-Metal Screws