Screws come in many sizes and can be used for all sorts of DIY tasks. Read more about which sort of screw you'll need for your particular job.

Uses for screws

As with nails, different types and sizes of screws are used for different jobs, but for everyday DIY you'll need only a small selection.

You need a screwdriver to drive screws, and to work successfully the screwdriver tip must match the size and shape of the recess in the screw head.

You can drive (and remove) screws by hand, or with a cordless screwdriver or drill.

 

Screwing wood to wood

Start by choosing a screw with a countersunk head that's long enough to pass through the piece you're fixing, and halfway through the piece you're fixing it to.

The screw head will be flush with the surface once the screw has been driven in.

Screws come in different diameters called gauge numbers, but for most jobs you'll need only two.

Gauge 8 screws up to 50mm long will be thick enough for most jobs; use a thicker gauge 10 screw up to 75mm long for heavier-duty fixings.

 

drilling holes

1. Mark where you want the screw hole in the piece of wood you're fixing. Fit a twist drill bit the same size as the screw shank in your drill, and drill a clearance hole right through the wood.

Place scrap wood beneath the workpiece so you don't drill into your workbench.

2. Exchange the twist drill bit for a countersink bit and drill the cone-shaped recess for the screw head in the mouth of the clearance hole.

It should be as wide as the screw head.

creating a clearance hole

3. Hold the piece of wood you're fixing in position over the piece you're fixing it to.

Push a nail (or a bradawl if you have one) through the clearance hole you drilled in step 1 to mark the screw position on the piece below.

Drill a pilot hole 2mm in diameter at the mark, to half the depth of the wood.

insert screw

4. Reposition the two pieces of wood and insert the screw through the clearance hole in the top piece so it enters the pilot hole in the piece beneath.

Tighten it fully with your screwdriver until the screw head is fully recessed in the countersunk hole.

 

Screwing metal to wood

Most metal fixtures—such as door handles, window catches, coat hooks and shelf supports—have countersunk holes for their fixing screws.

You can use a countersunk screw to attach them, but screws with raised countersunk heads look more attractive.

They're available in brass, chrome and stainless steel, and matching screws are often supplied with the fixture.

If you have to supply your own, make sure the screw shank will pass through the clearance holes in the fixture.

The screws should be long enough to pass halfway through the wood you're fixing into.

Door hinges are an exception; they're always fixed with countersunk screws.

Some metal fixtures—particularly those used out of doors, such as gate hinges—don't have countersinks, and are fixed with round-head screws.

The hemispherical screw heads sit proud of the surface.

Position fixture

1. Decide where you're going to position the fixture. Hold the fixture in position and mark each screw position on the wood in pencil through the clearance holes.

drill pilot hole

2. Drill a 2mm pilot hole at each mark, to half the thickness of the wood.

If you find it difficult to gauge the depth, use a guide on the drill bit—a strip of masking tape, for example. Stop when the guide touches the wood.

tighten fixture

3. Replace the fixture over the holes and drive in the screws. If there's more than one, only tighten them fully when you're sure the fixture is straight and level.

 

Screwing into metal or plastic

You may want to make a fixing into a metal or plastic surface—for example, to mount a roller blind to a PVC window.

You need a special self-tapping screw for this sort of job. The screw needs a pilot hole, and cuts its own thread as it's driven in.

Self-tapping screws are made from hardened steel and come with countersunk, raised countersunk and pan heads (the last resembles a roundhead screw, but with the head flattened).

 

Screwing into walls and ceilings

You cannot simply drive a screw into most walls or ceilings to make a fixing.

There are two exceptions: if you have a timberframed partition wall and the fixing position coincides with one of the vertical frame members, or if you're making a ceiling fixing directly into a joist.

Otherwise you have to drill a hole and insert a special fixing device to hold the screw in place.

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