Self-drilling screw + washer 6x25mm for trapezoidal rail mounting

It is the screw that drills its own hole in the roof sheet and, in the same movement, also plugs it. Under its head sits a rubber ring that flattens when tightened and stops the water. The tip is made of hard steel, so that it can pierce the sheet, and the rest of the body of stainless steel, so that it does not rust after the first winters.

It is tightened until the rubber washer is clearly seen compressed: neither less, because it would let the water through, nor more, because the sheet would deform and exactly the sealing being sought would be compromised. The double thread screws it in faster and locks it better in the thin sheet, which would otherwise loosen over time under the cyclic loads from wind. One piece weighs 0,007 kg and is delivered in boxes of 100, and consumption is easy to estimate: in Corab kits 6 screws are usually used on each short SMT rail, and the T-021.2 kit of 1 kW contains, for example, 10 rails and 60 such screws.

Corab code M529, EAN 4005674672177, size 6x25 mm, double self-drilling thread, bimetal execution with A2 stainless steel, EPDM sealing washer included, net mass 0,007 kg/pc, packaging 100 pcs. The drilling tip and the first threads are made of hardened steel, the body of stainless steel: the construction avoids both the impossibility of drilling with pure stainless steel and the rapid corrosion of a screw made entirely of carbon steel exposed to the weather. Intended for fastening SMT trapezoidal rails directly into the roof covering sheet.

Who it suits

Suitable for the installer who mounts rails on corrugated sheet or on sandwich panels and needs the consumable part, by the box.

Terms explained

• Bimetal: Screw made of two metals: a tip of hard steel, which cuts the sheet, and a body of stainless steel, which resists rust.
• EPDM washer: The rubber ring under the screw head, which compresses in a controlled way and seals the hole.
• SMT rail: The short aluminium profile that is placed across the sheet corrugations and onto which the panels are fastened.

Technical specifications

Recommended applications

• Fastening SMT trapezoidal rails into the roof sheet
• Mounting photovoltaic systems on corrugated metal coverings and sandwich panels
• Sealed fastenings in thin sheet, permanently exposed to the weather
• Consumable element in Corab T-021 type kits for trapezoidal sheet

Technical details

Specifications confirmed from the manufacturer's datasheet

The Corab M529 self-drilling screw is the standard fastening element for attaching SMT trapezoidal rails directly into the roof sheet. It has the size 6x25 mm, double thread and is delivered together with the EPDM sealing washer. The EAN code is 4005674672177, the net mass is 0,007 kg per piece, and the standard packaging contains 100 pieces.

The execution is bimetal, with the part in contact with the outside made of A2 stainless steel: the drilling tip and the first threads are of hardened steel, which pierces the sheet, and the screw body is of stainless steel, for long-term corrosion resistance in an outdoor environment. This construction avoids both the problem of the pure stainless steel screw, which cannot drill the sheet, and the rapid corrosion of a screw made entirely of carbon steel exposed to the weather.

The double thread increases the driving speed and improves locking in thin sheet, reducing the risk of loosening over time under cyclic loads from wind. The EPDM washer compresses in a controlled way under the screw head and ensures the tightness of the penetration; tightening must be done until the visible compression of the gasket, without over-tightening, which would deform the sheet and compromise the sealing.

In Corab kits for trapezoidal sheet 6 screws are usually used on the short SMT rail; for example the T-021.2 kit of 1 kW contains 10 rails and 60 such screws.