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What is Countersinking?


What is countersinking?

  Pilot hole and a countersunk hole in two pieces of hardwood  

Countersinking involves enlarging the rim of a pilot hole.


Countersinking is especially necessary when working with hardwoods.


Why countersink?

  Countersunk hole and a countersunk screw  

You should only need to countersink a hole when working with countersunk screws. Countersinking a pilot hole allows a countersunk screw to sit flush with the surface of the material, giving your work a neat finish.

  screw torn work surface  

Without countersinking the hole, the screw may tear the fibres of the material, creating a rough work surface.


Countersink bits

  Countersink drill bit with a round shank  

Countersinking is done using a countersink drill bit; an example is shown on the left.


Most countersink drill bits have round shanks, which means they can only be used in chucks with 3 jaws. (Most cordless drill drivers will accept them but not most cordless screwdrivers.)

  countersink drill bit with a hexagonal shank  

If you are using a cordless screwdriver, ensure you select a countersink drill bit with a hexagonal shank; an example is shown on the left.

  Pilot drill bit with the ability to countersink and a hexagonal shank  

You can purchase bits that are able to drill a pilot hole as well as countersink it; an example is shown on the left.


These types of pilot drill are also available to buy with hexagonal shanks, for use in a cordless screwdriver.


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