12g (5.50mm) x 39mm Top Grip NEO Surfmist Hex Flange (5/16") Coarse Metal Roofing Screw Galvanised

About Painted Metal Screws

Painted self-drilling metal screws with colour-matched powder-coated heads, used to fix coloured sheet metal cladding (Colorbond and equivalents), fencing infill, shed sheeting and roofing to metal framing. Stocked in two head styles to match the application: hex flange (driven with a nutsetter) for cladding and roofing where a sealing washer gives weatherproof fixing, and wafer-head Phillips for fencing and shed sheeting where the flat head sits low against the sheet for a tidy finish. Standard colours include Basalt, Cottage Green, Deep Ocean, Monument, Shale Grey, Surfmist, Wallaby and Windspray. AS 3566 Class 3 corrosion rating; Bremick Revolution B8 coating available on selected sizes for higher coastal exposure.

Recommended use Galvanising has been the proven outdoor coating for fasteners for decades - external building work, structural framing, fencing, decking, retaining walls, marine and coastal construction, anything exposed to weather. Newer coating advances - Class 4, Bremick B8 and Hobson X9 - build on this with longer service life and better resistance to severe coastal and industrial sites.

Frequently Asked Questions

Material & Coating

Galvanised Screws come with different coatings for different environments. The Australian standard for screws is AS 3566 - the higher the class, the more rust protection. Class 4 is our preferred minimum.

Class 4 / Bremick B8 / Hobson X9 This SKU is sold under two brands - Bremick and Hobson - with their premium coatings on a Class 4 base. Bremick's B8 and Hobson's X9 are both rated above Class 4 and protect against severe coastal and industrial environments, including beachfront work within 150 metres of breaking surf. Whichever brand arrives, the protection is equivalent.

Important Match the coating to where you're building. Class 4 is our preferred minimum and handles severe coastal sites within 1 km of the surf. For beachfront work (within 150 metres of breaking surf) or heavy industrial sites, use Bremick B8 or Hobson X9. See our full coating comparison, or send us your postcode and we'll match it for you.

Thread Pitch & Terminology

Thread Pitch (TPI)TPI stands for "threads per inch", which literally means the number of threads within each inch on a screw, a bolt or a fastener. To determine the TPI of a screw, count the number of threads contained within an inch of length on the fastener. If the screw is less than an inch long, count the threads in half an inch and multiply by 2. The higher the number, the finer the thread. For self-tapping and self-drilling screws into metal, a coarse thread (lower TPI, typically around 10 to 14) is better for thinner sheet metal - the bigger thread bites and holds in a thin section. A fine thread (higher TPI, typically around 24 to 32) is better for thicker steel, where the closer thread spacing gives more engagement per fastener and a stronger hold against pull-out.

Need every size? See our full screw gauge sizing chart for every standard gauge with diameter in mm and inch.

How to Measure

Fastener Length This product has a head that sits on top of the material, so the length is measured from directly under the head to the tip of the thread. The head itself is not included in the size.

Thread Length On a screw the thread length runs from the start of the unthreaded section (called the shank) to the end of the thread. To view the thread length for this product, select a length above.

Thread Length & Drill Point

Length of thread Always choose a self driller with enough threads to fully engage in the base metal. For attachments to 1/4" base steel, a self-drilling screw should have at least 1/4" of threads. It is helpful, but not critical, that the threads also engage in the material being fastened. The head of the fastener provides the bearing force for the material being fastened, while the threads provide the clamping force in the base material.

To determine thread length Before buying countersunk screws, it is recommended to work out the overall length you need. Because the overall length includes head height and drill point length you have to add the two together then minus that from the overall length to get the approximate thread length. For example: a 10g-16 x 35mm countersunk self-drilling screw has a 4mm head height and a drill point of approximately 12.50mm. This equals 16.50mm, so on a 35mm long screw you are left with approximately 18.50mm of thread. This detail is often overlooked, and it is only when the screws arrive that you find they are too short and your project is delayed. All this data and other specifications is on the specifications table above. Measurements are approximate and do vary between batches and suppliers; if critical, always check with us prior.

Drill point style A twist-drill style hardened point for fast driving into light-gauge sheeting, cladding panels, sections and assemblies. The length of the drilling flutes determines the amount of drilling swarf that can be expelled, and therefore the depth of metal that can be drilled.

Resources

Pricing & Delivery

Includes GST, a Tax Invoice and Free Standard Delivery anywhere in Australia.

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Disclaimer

Technical data Researched and compiled from numerous industry sources for the sole purpose of providing basic information. All material is advisory only and its use by anyone is entirely voluntary. Reliance on it for any purpose by anyone is at the sole risk of that person, and Bolt and Nut Australia is not responsible for any loss, claim or damages arising therefrom. In developing this information, Bolt and Nut Australia has made a determined effort to present it accurately.

Measurements Sizes are taken from supplier catalogues or hand-measured and should be used as a guide. Minor variation between batches is normal. Stock is sourced from various suppliers, so differences may exist between batches in thread length, markings, appearance or finish.

Product Photos & PDF Data Sheets Represent the product type, not exact size. PDFs are a reference guide only. Specifications may change without notice.

If you see any problems with any of our specifications or you require additional information please contact us.