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Tips on how to use screwdrivers most effectively.

Summary

Using a screwdriver is easy - who needs a page like this? You will often get away with using the wrong screwdriver or not using it properly, but you can easily damage the head making it extremely difficult to remove an obstinate screw.

Safety

Screwdrivers have pointy ends and although not sharp like a knife, they can cause serious injury if they slip or are misused.

Which way to turn it?

Those who are unaccustomed to using a screwdriver are often uncertain which way to turn it.

The easy way to remember is that it's like a tap (not the modern quarter-turn type):

• You turn a tap anticlockwise to open it and release the flow of water.
  • You turn a screw anticlockwise to undo it and release whatever it's holding.
• You turn a tap clockwise to turn it off and hold the water supply.
  • You turn a screw clockwise to tighten it and hold whatever it's fixing.

How to use a screwdriver

Removing a screw

First of all, make sure you're using the right type and size of screwdriver (see next section), particularly if the screw might be tight, or needs to be well tightened.

Make sure you're holding the screwdriver straight and not at an angle to the screw.

Press hard! If you can't turn the screw easily, PRESS VERY HARD!!

If the screwdriver isn't straight or you don't press hard enough to prevent it slipping you are likely to damage the screw head. This is known a "camming out". It can be almost impossible to remove a damaged screw.

If the screw is rusty you may be able to loosen it by applying a little WD40 to the thread and leaving it to soak in.

Inserting a screw

When inserting a screw it's very important to make sure it's straight otherwise you can get a "crossed thread" which will damage the screw or the threaded hole, or both.

If you have any difficulty at all in getting the screw to engage with the thread of the hole, first of all turn it anticlockwise (as if undoing it), pressing gently. You should feel a little click as the first thread of the screw engages with the first thread of the hole. Immediately start turning it clockwise to tighten it.

You can practice this on a jam jar, or any kind of container with a screw top. People often put the lid on crooked so that the screw thread doesn't engage properly and the container doesn't seal. Turn the lid anticlockwise until you feel the click, then tighten it as normal.

A screw should be well tightened, but never so much that the screwdriver slips and damages the screw head.

Types of screw head

There are many types of screw head but just a few common ones, and each comes in a range of sizes. With some types the wrong size won't work at all, and with the more forgiving types the wrong size will at best give you sub-optimal leverage and at worst will damage the screw head.

These are the types of screw you are most likely to come across.

Slotted

The commonest and oldest type of screw head just consists of a slot, and is driven by a flat bladed screwdriver. It has the disadvantage that the blade easily slips out of one end of the other of the slot. Choose a screwdriver with a blade which best fits both the width and length of the slot.

In a tamper-resistant version the slot is interrupted in the centre, making it impossible to use a standard flat screwdriver. This requires a special screwdriver with a slot in the centre of the blade. These are quite often seen in domestic electrical and kitchenware items.

Phillips

This is a common form of cross-head screw, not to be confused with the Pozidriv. Phillips screwdrivers come in sizes 000, 00, 0, 1, 2, 3 (in increasing order of size), sometimes prefixed with "PH", to distinguish from Torx. and you should use the right size if possible.

Pozidriv

Superficially similar to a Phillips screw, the Pozidriv is distinguished by the tick marks at 45 degrees and is designed to allow greater torque to be applied without risk of camming out. Pozidrive screwdrivers come in sizes 0 - 5, prefixed with "PZ".

A Pozidriv screwdriver has a less pointed tip than a Phillips and so it is inadvisable to use a Phillips screwdriver on Torx screws as the screw had is liable to be damaged if more than minimal torque is applied.

Torx

Common in electronic equipment, a Torx screw requires exactly the right screwdriver and correctly used, gives very good resistance to cam-out. Torx screwdrivers come in a wide range of sizes, from T1 (snallest) up to T100, the smaller sizes from around T6 to T10 being commonest in electronic repair.

A tamper-resistant version has a small pin in the centre of the recess, requiring a screwdriver with a corresponding hole in the centre of the tip.

Hex

These have a hexagonal recess in the head and require either a hexagonal screwdriver or an Allen key, which is simply a piece of hexagonal hardened steel bent into an L-shape. Self-assembly furniture and other items often uses hex screws and will come with an Allen key.

Pentalobe

At first glance resembling a Torx screw, these have 5 lobes instead of 6. They are commonly used by Apple as a tamper-resistant screw, but the screwdrivers are readily available. If you order a replacement iPhone battery or screen it will often come with a cheap pentalobe screwdriver.

Others

In addition to the above, you may come across various other types of screw less often, listed in the Wikipedia article List of screw drives.

Choosing your screwdrivers

However many screwdrivers you have, from time to time you may find you haven't got the right one for the job. A carefully chosen selection, though, will satisfy nearly all you needs. There are several options.

External links

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