Bi-Metal Screws
Bi-Metal Hex Washer Head Self-Drilling Screw
SS304 or SS316 body welded to an SS420 drill tip, indented hex washer head with SS + EPDM washer, M4.8–M7.
M4.8SS304 or SS316
Bi-Metal Screws
Stainless steel cannot be hardened enough to drill steel, and hardened carbon steel rusts. A bi-metal screw solves both: a 304 or 316 stainless body is friction-welded to a hardened carbon or martensitic tip that drills the hole and then sits on the inside of the joint, out of the weather.
Bi-Metal Screws
Bi-Metal Wafer Head Self-Drilling Screw
SS316 + SS420 wafer head Phillips screw with ceramic coating, 5.5 × 40 mm standard, for aluminium-to-steel joints.
5.5 × 40 mmSS316
Bi-Metal Screws
Bi-Metal Pan Head Self-Drilling Screw
SS316 + SCM435 pan head Phillips screw, 5.5–14 × 25/32/38 mm, salt spray 500–3,000 h.
5.5–14 × 25 / 32 / 38 mmSS304 or SS316
Bi-Metal Screws
Bi-Metal Flat Head Screw with Wings
SS316 + SS420 countersunk reamer screw with wings, ceramic coated 500/1,000 h, for timber or board on steel.
5.5 × 40 mm standardSS316
Bi-Metal Screws
Bi-Metal Solar Mounting Screw
SS304 + SS420 self-drilling screws for PV mounting rails and clamps, ceramic coated 1,000 h.
DINSS304
Bi-Metal Screws
Bi-Metal Pan Head Star Drive Roofing Screw
SS304/316 + AISI 420 pan head Torx screw with EPDM washer, 16–400 mm, for standing seam and solar.
SS304 or SS316
Buying guide
How to specify bi-metal screws
Three decisions that prevent most problems on site.
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.
Applications
Projects using bi-metal screws
Bi-Metal Screws: common questions
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.
Request for quotation
Quote for bi-metal screws
Tell us the screw, size and quantity. A sales engineer replies within one business day with price, lead time and a sample offer.
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