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Nails, screws & wall plugs buying guide

Introduction

Clout nails, lost-head nails, coach bolts, security screws, hammer-in plugs - the world of nails, screws and wall plugs can be daunting, so if you're going to do the job, make sure you use the right fixing.



Screws are usually made of mild steel, but hardened steel, stainless steel, solid brass and steel plated with chromium or brass are also available, as are galvanised rust-proof screws for outdoor use.

Anatomy of a screw

A screw has a head, a shank and a thread. Its length is measured from the pointed tip of the thread to the part of the head lying flush with the surface it's screwed into. The gauge is the diameter of the shank. Raised-head screws have heads that sit above the surface, countersunk screws have heads that are flush with or sink below the surface. Screws can have slotted or crossed heads - cross-headed screws being easier to drive in than slot-headed ones, especially with a power screwdriver.

Screw gauges

The imperial system of screw gauges ranked shank diameter as a number from 1 to 20 - the higher the gauge, the bigger the screw. The metric equivalents are not nearly so user-friendly, but this is how screws are now increasingly sold. Use this handy table as a guide:

 
Gauge   Clearance hole Pilot hole
Metric Imperial    
2mm 2 2.5mm 1.6mm
2.5mm 3 3mm 1.6mm
3mm 4 3.5mm 2mm
3.5mm 6 4mm 2mm
4mm 8 5mm 2.5mm
5mm 10 5.75mm 3.5mm
5.5mm 12 6.5mm 3.5mm
6.5mm 14 6.5mm 4mm

Types of screw

Carcass screw

Has a thick shank and a coarse thread, which can be useful for securing chipboard.

Chipboard screw

A deep thread extends right up to the head, making it good for wood as well as chipboard.

Coach bolt (cup square bolt)

A square neck under a domed head locks into the wood as the nut is tightened.

Coach screw

Has a square or hexagonal head that's driven in with a spanner. Gives a very strong, heavy-duty fixing.

Countersunk woodscrew

This traditional unhardened woodscrew has a single thread, and needs a pilot hole and shank-clearance hole to be drilled before it's fitted.

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Dry wall screw

A twin-threaded screw used for fixing plasterboard or fibreboard to timber studs.

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Hardened-steel woodscrew

Double threads make for fast insertion, with no need for a pilot hole if screwing into softwood.

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Masonry screw

A strong screw that can be driven into masonry without using a wall plug.

Raised-head woodscrew

Used for decorative hardware fittings, this screw is countersunk to the rim of the head.

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Round-head woodscrew

Used for fitting decorative door furniture.

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Security screw

The shape of the countersunk head prevents the screw being removed once it's in place.

Self-tapping screw

Cuts its own thread in thin sheet metal and plastic.


A normal screw won't stay in masonry without a wall plug. The wall plug expands grip the sides of the hole when the screw is driven in, holding the screw securely in place. Ideal for use during a wide range of construction tasks, as well as for hanging shelves, pictures and mirrors around your home.

Moulded plastic wall plugs are produced on plastic 'trees', with the size of drill bit printed on the tree. Some manufacturers make different-sized wall plugs in different colours - but take care, as colours are not standard across all brands.

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Hammer-in plugs

These alternatives to wall plugs and screws are good for fixing timber battens to masonry. One type has a wall plug with a ready-fitted screw. It's inserted into a drilled hole with a hammer, then driven home with the screw. There's also a version of this designed for plasterboard. The other type has a flanged expansion sleeve fitted with a masonry nail.

types of wall plugs

Moulded plastic wall plugs

These have a split end and can be bought to take a range of screw lengths and gauges.

Moulded plastic wall plugs

Straight plastic plugs

These are tubes with ribs running lengthways. They take the screw thread only, so they have to be cut shorter than the depth of the hole.

Straight plastic plugs