Screw types explained comes down to matching the fastener to the material and the job. Wood screws grip timber, metal screws bite into steel, and decking screws resist weather outdoors. Choosing the right head shape, drive and gauge stops splitting, stripping and rust, giving you a stronger, longer-lasting fix.
Walk down any fastener aisle and the choice can feel overwhelming. Once you understand the four things that define every screw, though, the pick becomes obvious. Below we break down the common screw types, then explain sizing, heads and drives so you leave with exactly what your project needs.
What are the main screw types?
Most jobs around the home come down to a handful of screw families. Each is engineered for a particular material and set of conditions.
Wood screws
Wood screws have a coarse, aggressive thread that grips timber fibres, usually with a smooth shank near the head so two pieces of timber pull tightly together. They suit furniture, framing, skirting and general carpentry. A good range of them sits in our hardware fasteners range for indoor timber work.
Metal and self-drilling screws
Metal screws have a finer thread and a hardened point. Self-drilling (Tek) screws add a small drill-bit tip so they cut through steel without a pilot hole, making them ideal for roofing, brackets, colorbond and light steel framing.
Decking screws
Decking screws are built for the outdoors, with corrosion-resistant coatings or stainless steel, a countersinking head and often a thread designed to pull boards down without popping. Always choose an exterior-rated screw for decks, pergolas and fences.
Chipboard, MDF and multipurpose screws
Chipboard screws (often called multipurpose or construction screws) have a fully threaded shank and a sharp point that reduces splitting in engineered boards. They are the everyday all-rounder many DIYers reach for first.
How are screw sizes measured?
Australian screws are described by two numbers: gauge (the shank diameter) and length in millimetres. A screw labelled 8g x 40mm is gauge 8, forty millimetres long.
Gauge runs from thin (4g, 6g) up to heavy (10g, 12g and beyond). Higher gauge means a thicker, stronger screw. As a rule, the screw should penetrate at least twice the thickness of the material you are fixing through, without punching out the far side.
Thread pitch matters too: coarse threads grip soft timber and boards, while fine threads suit hardwood and metal. When in doubt, match the screw to the density of what you are driving into.
Which head shape and drive should you choose?
The head sets how the screw finishes against the surface, and the drive determines the bit you need. Countersunk heads sit flush, ideal for a neat finish in timber. Pan and button heads sit proud and are handy for fixing brackets or thin sheet. Bugle heads spread load in plasterboard and decking.
For the drive, Phillips is common but cams out easily under load. Square (Robertson) and Torx (star) drives grip far better and are worth choosing for decking and structural work where you are driving hard with an impact driver. You will find drivers, bits and drills to suit in our broader tools and hardware range.
What about coatings, corrosion and outdoor use?
Coating decides how long a screw survives. Bright zinc is fine indoors but rusts outside. Galvanised offers better weather resistance for sheds and fences. For anything near the coast, in wet areas or in treated timber, step up to 316 marine-grade stainless steel, which resists rust and staining the longest.
Treated pine and hardwoods can react with cheaper coatings and cause corrosion, so stainless is the safe choice for decks and pergolas. When you need a fully corrosion-proof fixing that doubles as a bolt, the Zenith M5 x 32mm 316 stainless steel countersunk bolt and nut set is a neat, marine-grade option for through-fixing brackets and fittings.
Screw types at a glance
| Screw type | Best for | Thread | Typical finish |
|---|---|---|---|
| Wood screw | Furniture, framing, joinery | Coarse, partial shank | Zinc or countersunk |
| Chipboard / multipurpose | MDF, particleboard, general use | Full coarse thread | Zinc |
| Decking screw | Decks, pergolas, fences | Coarse, countersinking | Coated or stainless |
| Self-drilling (Tek) | Steel frame, roofing, brackets | Fine, drill point | Galvanised |
| Stainless bolt and nut | Through-fixing, wet/coastal areas | Machine thread | 316 stainless |
Do you always need a screw, or will a staple do?
Not every fixing job calls for a screw. For attaching insulation, underlay, fabric, fly wire or lightweight sheet to timber, a staple gun loaded with wide crown staples is faster and leaves a lower profile. Staples spread their grip across the crown, which is kinder to thin materials.
For general tacking around the house, the PowerFit 10mm wide crown staples handle lighter jobs, while the longer PowerFit 16mm wide crown staples bite deeper for thicker underlay and heavier fabric. Both are electro-galvanised for indoor durability.
Care and usage tips
- Pilot hole hardwoods to prevent splitting, especially near board ends.
- Match the bit exactly to the drive to avoid stripping the head.
- Keep like coatings together: do not mix zinc screws with stainless fittings outdoors, as they can corrode.
- Do not overdrive; stop when the head sits flush to keep full holding strength.
- Store screws dry in labelled containers so you can grab the right gauge next time.
Once you can read a screw by its type, gauge, head and coating, buying the right one becomes second nature. Keep a small assortment of the common sizes on hand, add corrosion-proof options like the Zenith stainless bolt set for outdoor work, and you will be ready for almost any fixing job that comes up.
Frequently asked questions
What do the numbers on a screw box mean?
The first number is the gauge, which is the shank thickness, and the second is the length in millimetres. For example, 8g x 50mm is a gauge 8 screw, fifty millimetres long. Higher gauge means a thicker, stronger screw. Length should let the screw grip firmly without poking out the far side.
Can I use wood screws for decking?
It is best not to. Standard wood screws usually lack the corrosion resistance and countersinking head that outdoor decks need. Use a proper decking screw or 316 stainless steel, which resists rust in wet conditions and treated timber. The right coating stops staining and keeps boards secure through years of weather.
What is the difference between Phillips, square and Torx drives?
They describe the shape the driver bit engages. Phillips is common but slips (cams out) under heavy load. Square (Robertson) and Torx (star) grip far better, so the bit stays seated when driving hard. For decking and structural work with an impact driver, square or Torx will save you stripped heads.
Do I need to drill a pilot hole before screwing?
For softwoods and engineered boards, usually no, especially with self-piloting screws. For hardwoods, near board ends, or when driving large gauges, a pilot hole prevents splitting and makes driving easier. Drill the pilot slightly narrower than the screw shank so the thread still bites firmly into the timber.
