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What is the cordless impact driver chuck size?

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When selecting a cordless impact driver, you will probably come across the term ‘chuck size’. This refers to the maximum shank diameter the chuck will accept.

What is the shank?

Shank of a bit holder, screwdriver bit and drill bit The shank is the part of a screwdriver bit, drill bit or bit holder that is actually held in the chuck.

Screwdriver bits and bit holders all have hexagonally-shaped shanks, while drill bits tend to have cylindrical, also known as ‘straight’ shanks.

Grey hexagon with a double ended arrow across the centre

How do you measure the shank diameter?

For hexagonal shanks, the diameter is measured across the flats.

Grey circle with a double ended arrow across the centre For straight shanks, the diameter can be taken from any point around the circumference.
Most screwdriver bits have a 6.35mm diameter shank Most cordless impact drivers have 6.35mm (¼”) hexagonally-shaped chucks. This means that they can only accept bits with hexagonal shanks with 6.35mm diameters.

Most screwdriver bits have 6.35mm hexagonal shanks, whereas a lot of drill bits will have straight shanks of varying sizes.

Types of drill bit with hexagonal shanks These days, you can purchase a wide variety of drill bits with 6.35mm hex shanks. However, you may not be able to use any old drill bit you have at home in your cordless impact driver.

What chuck size do you need?

Chuck on a cordless impact driver Quite simply, larger chucks can accept shanks with greater diameters.

When selecting a chuck, you should find out the shank diameter of the bits you want to use, and then choose your chuck size accordingly.

Wonkee Donkee says "Don’t forget - you should only use ‘impact bits’ in your cordless impact driver. These are specially made to withstand the high level of torque that the tool delivers"