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What are the parts of a brad point bit?

What are the parts of a brad point bit?

Shop for Brad Point Bits

Labelled diagram of a brad point bit indicating the different parts by name

Brad point

Labelled image of a brad point, which is usually found at the end of a wood bit. This is the part of the bit that gives it its name. The brad point, or brad, is sharp enough that its tip penetrates the surface of the wood and will not slide about when a hole starts to be drilled.
Two brad point bits with different sizes of brad point Brad point lengths can vary, but they always protrude further than the spurs. The longer the brad, the easier it is to drill at an angle, as more of the drill bit will already be secured inside the workpiece when the spurs start to cut, thus stopping it from slipping.

Brad point bit spurs

Brad point bit with the spurs labelled to indicate location Sharp spurs are located on the outside of the bit. As they rotate, they neatly sever wood fibre before the full pressure of the drill bit can cause it to splinter.
A clean borehole in a wooden workpiece This results in a very neat, clean hole.

Brad point bit lips

Diagram showing the location of a brad point bit's lip, between the brad point and the spur The lips of the brad point bit cut away any remaining material once the spurs have done their work. They act in a similar way to a chisel, cutting out the waste material and scooping it out of the borehole through the bit’s flutes.

Brad point bit flutes

Flutes on a brad point bit labelled to indicate location The flutes on a brad point bit are much wider than those found on a twist drill bit. This is to allow a large volume of shavings to escape the bore hole without clogging.
Diagram showing a 25 degree angle to illustrate the gradient of the flutes on a brad point bit Additionally, the angle of the flutes to the centre line of the drill is shallower on a brad point bit. Twist drill flutes are between 35 and 40 degrees from the centre line, whereas brad point flutes are only 25 degrees from the centre line.
A brad point bit in action, with wood shavings being cleared from the bore hole by the bit's flutes This means the flutes are more steeply inclined, allowing shavings to be ferried out of the borehole much more quickly.
Wood shavings can clog the flutes on a brad point bit, leading to a build up of friction

Why is it so important to keep the hole clear?

If waste material was allowed to stay in the bore hole, the flutes of a brad point bit would quickly become clogged. The trapped material would then rub hard against the edges of the hole.

Image illustrating the build up of heat due to friction from a clogged up brad point bit This would lead to a build up of friction, which in turn would create heat. The bit could very quickly reach a temperature where it would scorch the workpiece, or become too hot and lose its temper (hardness).
A piece of steel that has lost its temper and has turned blue as a result A bit that has lost temper is likely to be blunted very easily and is next to useless. Drill bits that lose their temper quite often turn blue, thanks to the chemical properties of the steel from which they are made. The smaller the drill bit, the more likely it is to overheat.

It is possible to re-temper a drill bit, although it may be worth looking at buying a new bit. For a step-by-step guide, see: How to re-temper a steel drill bit.

Brad point bit shank

An illustration of two of the types of shank commonly found on brad point bits, hexagonal and round The shank is the part of the bit that fits into the drill driver. Brad point bits are designed to work with a variety of different drill drivers. They usually have round shanks, but may be found with shanks of other shapes, e.g. hexagonal.

For more information, see: What are the different types of shank?

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