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What is a pilot hole?

 

What is a pilot hole?

 
         
  Pilot hole in a hard wood worksurface  

A pilot hole is a small hole drilled in material before a screw is inserted or a larger hole is drilled.

 
         
     

Why make a pilot hole?

 
  Picture of a drill slipping on a work surface  

To help prevent the drill bit slipping

When drilling large holes, the drill can slip or skid across the work surface, causing damage. Drilling a pilot hole with a smaller drill bit first will help to prevent slipping.

 

When you come to drill the larger hole, your drill bit can rest on top of the pilot hole, which will guide it into the material.

 
         
  Piece of wood splitting after a screw has been driven in without a pilot hole  

To help prevent the material splitting

When drilling large holes or driving large screws into wood or plastic, the material can split if a pilot hole is not drilled first.

 
         
     

Pilot drill bits

 
  Pilot drill bit  

To drill a pilot hole, you need a pilot drill bit. You can purchase pilot drill bits to use in a cordless screwdriver with a hex chuck or a cordless drill driver with a 3-jawed chuck.

 

Ensure you select the right size pilot drill bit. This will depend on the size of screw you want to insert, or the diameter of the hole you want to drill.

 
         
  A crew with the labelled shank width and the screws threads with a pilot drill bit with labelled drill bit width  

For driving screws

Select a drill bit that is the same width as the screw’s shank. This way, the drill bit will remove enough material to prevent splitting but will leave enough for the screw’s threads to bite into when its driven in. 

 
         
  A screw and pilot drill bit overlapped to check if they are the same width  

 You can check that the drill bit is the same width as the screw’s shank by holding it in front of the screw, and looking to see if they match.

 
         
     

Is a pilot hole always necessary?

 
  Pilot hole  

Generally, you should always drill a pilot hole unless you are carrying out rough construction with softwoods.