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Screw Glossary

 

Screw glossary

 
         
  A silver screw on a yellow and red star background  

When learning about screws, you may come across some of the following phrases:

 
         
  Wonkee Donkee says "Although they may sound confusing, don’t be put off, there is always a simple explanation"     
     
     

Alignment

 
  Screw driver bit positioned centrally in the drive of a screw  

When inserting or removing screws, you should ensure that the screwdriver bit is sitting correctly in the screw’s drive.

 

If you are using slotted screws, make sure that the screwdriver bit is positioned centrally in the drive on top of the screw’s head.

 
         
  Screwdriver bit sitting to the side of a screw's drive  

If the screwdriver bit is not sitting in the centre of the screw’s drive, it may not be able to turn the screw properly and could slip out, potentially causing damage to the screw or work surface.

 
         
  Screwdriver bit at a 90 degree angle to a screw head  

You should also try to ensure that the screwdriver bit sits in the drive at a 90 degree angle to the screw head.

 
         
  Screwdriver bit which has slipped from the screw head  

If you try to drive the screw at an angle, it may not engage with the screw correctly and could slip out, potentially causing damage to the screw or work surface.

 
         
  Self-centring screw drive with a screwdriver bit  

Nowadays, most types of drive are self-centring. This means that they are designed to make it easy for the screwdriver bit to sit correctly in the screw by guiding it into place.

 

On the left is an example of a screw with a Phillips drive, and a Phillips screwdriver bit. The Phillips design tapers down into the centre of the screw’s drive, guiding the screwdriver bit into it.

 
         
  Wonkee Donkee says "Slotted screws are not self-centring, which means it is easy for the screwdriver bit to slip out of the screw head"  
         

     

Flush

 
  A countersunk screw flush with the surface of the material and two screws not flush with the surface  

The term ‘flush’ is used when talking about screws with countersunk or bugle heads. When these types of screws are driven in correctly, they should sit ‘flush’, which means they are completely level and even with the work surface.

 
         
  A raised head screw and a domed head screw no sitting flush and a countersunk head screw and a bugle head screw sitting flush on a piece of material  

The only 2 types of screw head that can sit ‘flush’ with the work surface are bugle and countersunk. All other types of head sit above the work surface. 

 
         
     

Slipping

 
  A screwdriver bit slipping on a black screw  

When driving certain types of screws, the screwdriver bit can slip out of the screw head, when a lot of torque (turning force) is applied.

 

This is also known as “camming out”, and can result in the screwdriver bit damaging the screw head or the work surface.

 
         
  A cordless drill driver slipping on a piece of wood  

When drilling

The term ‘slipping’ can also refer to drilling applications. When working with large drill bits or materials with smooth surfaces, the drill bit can slip across the work surface when you first begin drilling.

 
         
  A black hammer with a rubber handle hitting a centre punch into a piece of wood  

You can help to prevent the drill slipping by using a centre punch. A centre punch is a tool used to make a small indentation on the surface of a material using a hammer.

 
         
  Drill bit sitting in the dent left by a centre punch  

The drill tip then sits in the small dent made by the centre punch, making it less likely to slip across the work surface once it starts turning.

 
         
      Wonkee Donkee says "My dad used to stick a piece of masking tape over the area he wanted to drill if he didn’t have a centre punch handy. This can also help prevent the drill bit from slipping"  

 

 

 

 

     

Stripping (a screw head)

 
  Damaged screw head in a piece of wood  

A stripped screw head is the term used to describe a screw that has been damaged by a screwdriver bit. Stripped screws are the result of a number of things:

 

  • General wear and tear

  • Using the wrong size or type of bit for the screw

  • The screwdriver slipping out of the screw’s drive and damaging its surface.

 
         
  Ruined stripped screw  

A stripped screw is usually a ruined screw. If a screw’s drive has become misshapen, it may be very difficult to remove.

 
         
  Small manual screwdriver with a blue handle  

How do you remove a stripped screw?

There are several things you can try in order to remove a stripped screw.

 

1. Use a manual screwdriver

If the screw is not badly stripped, you can try removing it with a manual screwdriver. This will give you more control over the speed at which you turn the screw and the pressure you apply.

 
         
  A thick wide elastic band in between the screw head and the screw driver  

2. Use an elastic band

Place a thick wide elastic band on top of the screw head and apply pressure to the screw, turning it slowly.

 

The elastic band should fill the gaps caused when the screw was stripped and provide enough grip to turn it.

 
         
  Two grey screw extractors one spiral-fluted and the other straight-fluted  

3. Use a screw extractor

If you still cannot remove the screw, you can purchase a screw extractor. The two most common types of screw extractor are spiral-fluted (left) and straight-fluted (right).

 

These tools require you to drill a hole in the top of the screw before inserting the screw extractor and turning it using the tap wrench.