Bi-Metal Countersunk Self-Drilling Screws (SS304 + SCM435)
The bi-metal countersunk self-drilling screw joins stainless or aluminum sheet to steel without pre-drilling and finishes flush with the surface. A corrosion-resistant 304 stainless head and shank are friction-welded to a hardened SCM435 drill point, combining stainless-grade weathering performance with the drilling capability of alloy steel. Manufactured by an experienced bi-metal screw supplier for roofing, solar and cladding projects.
Features and Benefits
- 304 stainless head and shank for lasting corrosion resistance at the exposed surface
- Hardened SCM435 drill point drills steel up to 2 mm in one pass — no separate drilling or punching
- Countersunk head sits flush, leaving a smooth finish on architectural panels and flashings
- Friction-welded joint tested per batch for weld torque — no point loss in service
- Phillips drive with sharp cutting recess — stable driving without cam-out
Typical Applications
- Stainless and aluminum roofing to steel substructures
- Solar mounting rails and module clamps
- Architectural cladding, fascia and flashing details
- Signage, ductwork and equipment housings
- Any application where a flush stainless face meets a steel frame
Model Specifications
| Thread Size | Drilling Capacity | Length Range | Drive | Material |
|---|---|---|---|---|
| #8-18 (4.2 mm) | steel up to 2.0 mm | 13-38 mm | PH2 | SS304 + SCM435 |
| #10-16 (4.8 mm) | steel up to 2.0 mm | 16-50 mm | PH2 | SS304 + SCM435 |
| #12-14 (5.5 mm) | steel up to 2.0 mm | 19-65 mm | PH3 | SS304 + SCM435 |
Material and Performance
- Head and shank: AISI 304 austenitic stainless steel, passivated bright finish
- Drill point: hardened SCM435 alloy steel, HRC 50-58, friction welded and batch-tested
- Corrosion resistance: the stainless body matches aluminum and aluzinc panels without galvanic attack
- Standards: manufactured to DIN 7504 K equivalent geometry; ISO 9001 quality system
Installation Guidelines
- Select the point size against the total steel thickness — the point must drill the full stack before threading starts.
- Drive with a Phillips bit at controlled speed (max. 2,500 rpm), keeping the tool square to the surface.
- Stop when the countersink seats flush with the sheet face — do not overdrive, which enlarges the recess.
- For stacked sheets with an air gap, confirm the combined thickness stays within the drilling capacity.
- In high-corrosion sites, pair with a stainless-compatible sealing washer where the drawing requires weather-tightness.
Why Source from BuildFastener
Weld-line integrity, drill capacity and hardness are checked on every lot. We stock common roofing and solar sizes and support custom lengths and head markings for OEM programs. Request samples and test the driving feel against your current brand.
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