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Use the Right Screwdriver

By: Chris Hogan MSc - Updated: 18 Sep 2012 | comments*Discuss
 
Screw Screwdriver Blade Bit Slot

Many DIY enthusiasts will be familiar with the sinking feeling as a screwdriver slips out. Or maybe you strip the head, it goes round and round without the screw moving and know you're never going to get that screw out without a drill, a saw and a large hammer.

Get to Know Your Screws

But it doesn't have to be that way and the key is to use the right screwdriver in the first place. It doesn't matter whether you're using a cordless screwdriver with bits or a set of screwdrivers going back to your granddad's time, if you don't use the right screwdriver to fit the screw head then you'll be in trouble.

And this applies to screwing things in as well as unscrewing them. If you use the right screwdriver to tighten a screw then you're less likely to strip the head in the first place. Then it will be so much easier to unscrew later.

Different Screw Head Types

There are three main categories of screw head configurations, although there are many different sizes and shapes within each category. The main categories are:

  • Slotted – single slot across the head, traditionally used in carpentry and joinery.
  • Crosshead – widely used but not often where the screwhead will be seen.
  • Socket or Hex – sunken specially shaped holes such as Allen or Torx heads.
We'll deal with the third category first as there's little to say about them. As long as the correct sized key is used and the hole in the head is clear of debris, it is very difficult to strip the heads. The sockets for Allen keys are hexagons, Torx have a six pointed star and you may come across others.

Don't Mix Up Your Crossheads

The various types of crosshead screws can cause confusion and it's vital to know the different types. A simple crosshead is a slot screw with second slot at ninety degrees to it. An ordinary slot screwdriver is used for these, they are just a bit more resilient because if one slot is chewed up there's another one that can be used.

Then there are the sunken crosshead screws such as Phillips, Posidriv and Supadriv. There are subtle differences between them but the two most important things are to get the right size of screwdrivers and not to mix the types. If you look at a Phillips head screw it is a cross shape whereas the other two have a second, smaller cross offset against the larger one, so they appear to have eight points.

Know Your Crosshead Styles

These were developed for power driving as they are all less likely to slip out like a slot bit can. But if you use a Posidriv or Supadriv screwdriver on a Phillips screw head, or vice versa, it is highly likely that the internal arms of the cross in the head will be smoothed off as soon as any real force is applied.

This will severely dent your chances of getting it out. So insert the screwdriver carefully then apply gentle force one way then the other. If the screwdriver wobbles or slowly comes out of the screw, then it’s the wrong size or type.

Slot Screws

Finally, slotted head screws can be the trickiest. It's tempting to think that any flat-bladed screwdriver or bit will drive any screw as long as it's narrow enough to get in the slot. But this is not true and can turn a simple DIY weekend into a cursing fest.

First the width. The blade of screwdriver has to be a snug fit. If it's too fat, obviously it won't fit into the slot. But it is too thin then as it turns it will gouge into the sides of the slot, widening it and rounding the edges of the screwdriver blade.

But then you need to think of the width of the screwdriver or bit width too. If the blade is too wide it could damage the wood around the screwhead as you to try to screw it in or unscrew it. If it is too narrow you will get the rounding effect and in extreme circumstances it can bend or break the edges of the screwdriver blade.

Know Your Screw

So the key points are to know the type of screw you are dealing with and to make sure you have the right type and size of screwdriver or bit. And remember, it's often quicker in the long run to go down to the shop and buy the right tool than have to deal with the consequences of using the wrong one. A good DIY store should be able to help you understand the different screw types.

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