Class 3 And Class 4 Hex Head Self Drilling Screw (SDS) For MS Roofing & Cladding

Self Drilling Screws (SDS) are sometimes mistakenly called as Self Tapping Screws (STS). As the name indicates self-drilling screws can drill themselves into the metal roofing which saves a lot of time and effort. They are one of the important fasteners for metal buildings, we usually use class 3 and / or class 4 hex head self drilling screw to fix metal roofing & cladding profiles to steel purins, the common Installation methods are Crest Fixing, Cladding Fixing/ Valley Fixing, Clip Fixing and Side Lap Fixing (Stitching). Self Drilling Screws (SDS) are a small part of the costs of the roof construction,  however, a poor-quality self-drilling screw can result in enormous costs if it is badly designed or made of inferior material. 

UnionSSM does not manufacture self-drilling screws, but purchases them all. With nearly 30 years of experience in steel structures, UnionSSM has selected many high-quality self-drilling screws special for metal cladding, including but not limited to well-known brands such as ITW- Boustead. Self-drilling screws supplied by UnionSSM can be used with confidence.

1. Screw Heads- Universal Hex Head, easier accessibility from all angles. Color-matched head cap are available to enhance the aesthetics of roofs and walls.
2. Screw Washer- Special EPDM washer that control the balance of carbon black, can effectively prevent UV aging and chemical corrosion, so that to achieve a reasonable service life; it provide an excellent waterproof seal— even under the most severe weather conditions— if properly installed. The non-conductive design can also slow down the rate of metal roof and wall corrosion.
3. Top Tapping- The special thread design avoids the concave deformation of the profiled metal plate during nailing, it reduces the occurrence of water accumulation and corrosion；it also makes the profiled metal plate and the Screw Washer closely attached to achieve the best sealing effect.
4. Coating - High-efficiency anti-corrosion alloy polymer coating, with mechanically deposited at room temperature to prevent "hydrogen embrittlement". The coating is denser and the bond is stronger. Compatible with any metal profile. Corrosion resistance, and carry out the real natural environment test.
5. Screw Protection Section - Effectively protect the coating from damage when the screw is drilled.
6. Tapping:The special thread design avoids the concave deformation of the profiled metal plate during nailing, it reduces the occurrence of water accumulation and corrosion；it also makes the profiled metal plate and the Screw Washer closely attached to achieve the best sealing effect.
7. Drilling: Powerful drill bit, strong drilling ability, easy and labor-saving Installation.

Notes: Product descriptions vary with brands and specific uses, please contact us for specific specifications.

AS 3566AS 3566 Self-Drilling Screws for the Building and Construction Industries (Australian Standard)

Corrosion Class Categories:

Class 1 - for general internal use, most drywall and chipboard screws are in this category
Class 2 - for general internal use, where significant levels of condensation occur. Electroplated ZINC is generally used to meet this class.
Class 3 - for general external use in mild and moderate industrial and mild marine applications. The Class is intended for roofing and cladding screws in standard applications. Fastener compliance used to be achieved by accelerated laboratory testing.
Class 4 - for external use in moderate and severe marine environments, classified in accordance with ISO 9223 as generally between 100m from the beach front to approximately 300m inland.

Setp 1: Choose the right Self Drilling Screw specification and Installation method according to the material of metal cladding system and Installation location.

The common Installation methods of self-drilling screws for metal enclosure systems are: Crest Fixing, Cladding Fixing/ Valley Fixing, Clip Fixing and Side Lap Fixing (Stitching).

Step 2: Properly driven: Driven the self drilling screw (SDS) straight; good penetration, gasket compressed firmly against the surface.

4 common causes of metal roof leaks around screws: below is a list of common causes of metal roof leaks. 

1. Choosing an incorrect screw 

2. Over–driven screws (Washer over compressed: EPDM washer squeezed too thin, Extends far beyond screw head)

3. Under-driven screws ( Washer under compressed: EPDM washer not compressed to form seal)

4. Misaligned or skewed drilling

Important Tips:

1. The trick to make it watertight is not to overdrive or underdrive the screws. If the screw is not tightened enough, moisture leaks around the washer. An overtightened screw squishes the washer too thin, which can also result in leaks.        

2. Replace worn sockets immediately if they cause the screw to wobble during Installation. Crookedly driven screws can cause water leaks. 

When you purchase metal roofing and walls in our company, we usually provide a complete set of self-drilling bolts according to the drawings, including detailed specifications and quantities and Installation drawings. In principle, this product is not sold separately.

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