Wood Screw Buying Guide
The Sticky Stuff Store Guide
Choosing the right wood screw makes every job easier, stronger and longer lasting. This guide explains the different types of wood screws, what the sizes mean, which head and drive to choose, and which screw to use indoors, outdoors and in hardwoods.
Which Wood Screw Do I Need?
Start with where the screw will be used. Moisture is the biggest factor in choosing the right screw.
| Job | Best screw | Shop |
|---|---|---|
| Indoor joinery, furniture, kitchens, shelving | Yellow zinc | Timco Solo |
| High-volume trade work | Yellow zinc, trade box | Solo Industry Pack |
| Fences, sheds, garden furniture, bathrooms | A2 stainless steel | A2 Stainless |
| Coastal, marine, pools, constantly wet areas | A4 marine grade stainless | A4 Stainless |
| Oak, cedar and tannin-rich hardwoods | Stainless steel or brass | A2 Stainless |
| Antique furniture, visible decorative fixings | Solid brass | Brass Screws |
| Flat-pack and cabinet assembly | Carcass screws | Carcass Screws |
| Decking | Specialist decking screws | Decking Screws |
Wood Screw Materials & Finishes
Yellow Zinc
Best for: indoor, dry conditions
Hardened carbon steel with a protective zinc coating, often called "yellow passivated". Strong, low cost and the most popular choice for indoor work. Not suitable outdoors, where the coating breaks down and the screw rusts.
Shop yellow screwsA2 (304) Stainless Steel
Best for: general outdoor use
Won't rust in normal outdoor conditions, making it the go-to choice for fences, sheds, garden projects, bathrooms and kitchens. It won't react with timber and leave black stains.
Shop A2 stainlessA4 (316) Marine Grade
Best for: coastal, pools, constantly wet
Contains molybdenum for much better resistance to salt water and chlorine. Use near the coast, on boats and jetties, around pools and hot tubs, and anywhere screws stay wet.
Shop A4 stainlessSolid Brass
Best for: traditional and decorative work
Used on period furniture, cabinet making and hinges where the screw head is on show. Brass doesn't rust, but it's softer than steel, so always drill a pilot hole.
Shop brass screwsBlack Screws
Best for: black hinges and ironmongery
Black organic or japanned screws give a dark finish that blends in with black ironmongery, hinges and fittings.
Shop black screwsSilver Zinc
Best for: indoor, dry conditions
Silver (bright) zinc screws work in the same way as yellow screws and are also intended for dry, indoor use. Choose them when you prefer a silver finish.
Wood Screw Sizes Explained
Wood screws are measured as diameter x length in millimetres. For example, a 4 x 40mm screw is 4mm thick and 40mm long. Older imperial sizes use a gauge number for diameter, such as No. 8, which many people still search for.
| Metric diameter | Approx. imperial | Typical uses |
|---|---|---|
| 3.0mm | No. 4 | Small hinges, catches, thin boards |
| 3.5mm | No. 6 | Hinges, light fixings, cabinet backs |
| 4.0mm | No. 8 | General joinery, shelving, brackets, furniture |
| 4.5mm – 5.0mm | No. 10 | Frames, stud work, kitchen units, heavier timber |
| 6.0mm | No. 12 | Heavy-duty fixings and thick timber |
How long should my screw be?
Choose a screw around 2.5 times the thickness of the piece you're fixing, so most of the thread grips the timber behind. For example, to fix an 18mm board, use a screw of about 45mm to 50mm.
Fully Threaded or Part Threaded?
Shorter screws are usually threaded all the way to the head. Longer screws often have a plain shank near the head, which lets the screw pull two pieces of timber tightly together instead of holding them apart.
Wood Screw Head Types
Countersunk
Sits flush with or just below the surface. The most common head for general woodwork.
Double countersunk
A countersunk head with a second angle underneath, making it stronger and less likely to snap. Used on most modern multi-purpose screws.
Pan head
A flat underside that sits on top of the surface. Ideal for brackets, thin sheet material and fittings without countersunk holes. Shop pan head
Round head
A domed head that sits on the surface, often used decoratively. Shop round head
Raised countersunk
Sits in a countersunk hole with a slightly domed top, for a neat, decorative finish on hinges and fittings. Shop raised head
Wood Screw Drive Types
Pozidriv (PZ)
The most common drive in the UK. Small extra lines between the cross give better grip and less slipping. Most wood screws take a PZ2 bit.
Phillips (PH)
Looks similar to Pozi but has no extra lines. Using the wrong bit will slip and damage the head, so always match the bit to the screw.
Slotted
A single straight slot. Mostly used on traditional brass screws for an authentic period look.
Torx (TX)
A star-shaped drive with excellent grip and almost no slipping. Common on premium and decking screws. Shop premium screws
Single Thread vs Twin Thread
Most modern wood screws have a single deep thread for maximum grip. Twin-threaded screws have two threads running side by side, so they drive in roughly twice as fast. That makes them popular for chipboard and quick, repetitive fixing. Shop twin-threaded screws
Do I Need a Pilot Hole?
Modern wood screws have sharp points and often don't need a pilot hole in softwood, chipboard or MDF. You should drill a pilot hole when:
- Fixing into hardwoods such as oak, ash or beech
- Screwing near the end or edge of timber, where it could split
- Using brass or stainless steel screws, which are softer than hardened steel and can snap
- Using large-diameter screws of 5mm and above
Trade tip
The pilot hole should be about the same size as the solid core of the screw, not including the thread. For brass screws, drive a steel screw of the same size first, then replace it with the brass one.
Buying Tips
- Buy the right quantity: many of our screws come in packs of 50, 100 or 200, so you don't pay for screws you won't use.
- Buying in bulk? Trade boxes such as the Timco Solo Industry Pack of 1,000 bring the cost down to under 1p per screw.
- Not sure of the size? A mixed tray gives you the most common sizes in one handy box.
- Need faster driving? Premium screws such as the Timco C2 range drive faster and hold more strongly. Shop premium wood screws
Wood Screw FAQs
What is the most common wood screw size?
4 x 40mm and 4 x 50mm (No. 8) are the most widely used sizes for general DIY and joinery, followed by 5mm screws for heavier work.
What size screw is a No. 8?
A No. 8 screw is roughly 4mm in diameter. A No. 6 is about 3.5mm, a No. 10 is about 5mm and a No. 12 is about 6mm.
What screws should I use outdoors?
Use A2 stainless steel for most outdoor jobs such as fences, sheds and garden furniture. Near the coast, around pools or in constantly wet conditions, choose A4 marine grade stainless steel. Yellow zinc screws are for indoor use only.
Why do screws leave black marks on oak?
Oak, cedar and some other hardwoods contain tannins that react with plain steel, causing black staining around the screw. Stainless steel and brass screws don't react, so use those for tannin-rich timbers.
What's the difference between PZ and PH screws?
PZ (Pozidriv) and PH (Phillips) are cross-head drives that look similar but need different bits. Pozi has extra lines between the cross and grips better. Always use the matching bit to stop the head slipping or wearing.
Are chipboard screws the same as wood screws?
Modern chipboard screws are general-purpose wood screws. Their sharp, deep single thread works well in both solid timber and man-made boards such as chipboard and MDF.
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