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What is a chuck and how does it work?

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Chucks are used to hold the drill bit in place securely on the drill or brace A chuck is a mechanism by which the drill bit is secured to the drill or brace. There are several types of chuck found on hand drills and braces.

The most common examples of these are: split frame chucks, 2 jaw chucks, 3 jaw chucks and 4 jaw chucks.

How does a chuck work?

The main parts of a chuck are; Body, Sleeve, Ring nut, Jaws, Teeth and Key  2 jaw, 3 jaw and 4 jaw chucks all work on the same principle. The body of the chuck positions and guides the movement of the jaws as they are brought together or separated.

The sleeve, or shell as it is also called, rotates around the chuck’s body.

As the ring nut is turned the chuck body guides the movement of the jaws tightening or loosening on the drill bit. As the sleeve or shell is turned, the ring nut is also turned. The teeth of the ring nut interlock with the teeth on the jaws, so as the ring nut turns, the jaws are moved forward and together (direction of green arrows) or backwards and apart, guided by the body of the chuck.
Turn the shell of the chuck clockwise to bring the jaws together and tighten on a bit, Turn the shell of the chuck anti-clockwise to separate the jaws and release a bit The jaws of 2, 3 and 4 jaw chucks are separated or brought together by turning the shell on the outside of the chuck.

Looking head on at the jaws of the chuck, if the shell is rotated clockwise then the jaws are brought together clamping the drill bit in place, whereas rotating the shell anti-clockwise, will release the drill bit by moving the jaws apart.

Some chucks require a key to tighten them, Key, Teeth, Chuck Some chucks require the use of a key to turn the sleeve; these are called ‘keyed’ chucks. However, most hand drills and braces use a keyless chuck, where the sleeve or shell is tightened by hand.
Hand drills and braces are available with both keyless chucks and chucks that require a key. The advantage of having a keyed chuck on your hand drill or brace is that the key allows you to apply more torque to the chuck, clamping the jaws tightly and ensuring a firmer grip on the drill bit, reducing the chance of it slipping in the chuck.

However, you have to have somewhere to store the chuck key as they cannot be stored on the drill. Having the chuck key separate from the drill often leads to them being lost or being left away from the drill when you need them.

Types of chuck

Split frame chuck

Split frame chucks

A split frame chuck is normally only found on older hand braces as it is the simplest chuck design. The frame of the brace is split in half at the point where the drill bit is held and a thumb screw or wing nut is used to tighten the chuck around the drill bit.

 To tighten the jaws of a split frame chuck and clap a bit in your brace turn the wing nut clockwise, to release the bit turn the wing nut anti-clockwise As the wing nut is tightened, the two halves of the split frame chuck are brought together, tightening them around the drill bit.
Auger bits such as those with square tang shanks are designed for use in split frame and 2 jaw chucks Split frame chucks are designed to be used with square shank drill bits. This is because the square cut out shape in the split frame provides excellent grip of square shank bits but is not capable of sufficiently gripping a round shank.
2 jaw chucks are designed to hold square shank drill bits

2 jaw chucks

A 2 jaw chuck has two jaws that, when brought together, have a square cut out recess similar to the shape of a split frame chuck.

Like split frame chucks, they are designed to be used with square shank drill bits.

3 Jaw chucks are designed to hold round shank drill bits

3 jaw chucks

3 jaw chucks are the most common type of chuck on hand drills. They are designed to hold round and hexagonal shank drill bits securely in place.

4 jaw chucks can hold both square and round shank drill bits

4 jaw chucks

A 4 jaw chuck has the advantage of being able to hold both round and square shank drill bits.

What does the capacity or size of a chuck mean?

The chuck capacity is the maximum size drill bit shaft that can fit between the jaws of the chuck when they are fully opened The capacity or size of a chuck refers to the maximum size of drill bit that it can hold. So a brace that has a chuck with a 13mm (1/2″) capacity can secure a drill bit with a maximum shank size of 13mm (1/2″).

What is a self-centring chuck?

A chuck that is self-centring means that all the jaws within the chuck are brought together at the same rate.

When the jaws are tightened on a drill bit, it will be held in the centre of the chuck and not off centre. All chucks that are used on braces and hand drills are self-centring.