KS3 Design and Technology (D&T): Screwing components together

Screws, nuts and bolts are very useful for fixing components together. But let's have a look at the various options there are, and how you can use them to the best effect.

Screws are used to fix wooden components together or for fixing components to wood.

A screw has two diameters: the diameter of the shank, the solid part, and the outside diameter, which is measured around the spiral flutes of the screw.

Start by clamping your two wooden pieces together and drill a pilot hole. The diameter of the pilot hole should be the same as, or just slightly smaller than, the solid shank of the screw.

Now, on the top surface, widen the pilot hole to make a clearance hole. The clearance hole should be the same diameter, or slightly larger than, the outside diameter of the screw.

If you are using a countersunk screw, like this one, you should now use a countersink bit in your drill to create a bevelled recess in the surface.

Try to judge the depth of this so that the surface of the screw sits flush with the surface of the wood.

Now, the wood is ready for you to screw the pieces together.

If you are using coach screws, pan headed screws or round headed screws, you might want to use a washer to spread the force from the screw and prevent damage to the top surface of your wood.

To fix together non-wooden materials like metal, plastic or glass you will need to use nuts and bolts.

The most common nut is called a hex nut, but there are two other options for you to choose from and each has its own advantages.

A smooth, rounded dome nut will give you the nicest finish.

While a nylock is best if it's important that your nut doesn't come undone. The nylon plastic insert grips the bolt tightly and prevents accidental loosening.

You can spread the load of both the nut and bolt by using washers.

In addition to your standard washer, you can choose from penny or mudwing washers, which have a large diameter to spread the load and cover oversized holes; or sprung washers which also protect against vibrations.

The most common style of bolt heads are: hex, round head, cap head or countersunk, and you should use the one you think looks best on your finished item.

Once you have made your selections, you're ready to drill the holes into your materials.

It's best to drill the hole the same size, or slightly larger than, the bolt size.

So, if you're using an M4 bolt, you'll need to drill a 4mm hole.

Now clamp your materials in place and drill the hole from the top surface down.

Now all that's left to do is slide in your bolt and the washer, and attach the nut.