what-are-the-different-auger-bit-patterns

What are the different auger bit patterns?

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A selection of auger bits, all made according to different manufacturing patterns There is some variation between auger bits as several different inventors made improvements on the basic twisted auger design and patented them. The different designs are referred to as ‘patterns’, and are described below.

Russell Jennings

An example of a Russell Jennings pattern auger bit This is the most common pattern for auger bits and is widely seen as ‘standard’ for auger bit design. It features flat lips, and spurs that protrude from the bottom of the bit.
Example of an auger bit with double-twisted flighting The flighting on Russell Jennings augers is double-twisted, meaning the bit bores a neat hole.
Russell Jennings auger bit tip The term ‘Jennings’ can also refer specifically to the tip of an auger, describing them as having flat lips and spurs that point in the same direction as their guide screw. This means that it’s possible to have augers of a different type with Jennings pattern lips.
Advantages and disadvantages of Russell Jennings auger bits ADVANTAGES DISADVANTAGES
  • Bores a neat, clean hole
  • Small risk of deviation due to wood grain or imperfections in stock.

Irwin

An example of an Irwin pattern auger bit Irwin-pattern augers, also known as solid core augers, are single twist tools. Some have a unique extra half-spiral at their tip.
Image showing how the incomplete spiral flighting on an Irwin pattern bit joins to the main part of the bit The extra spiral exists solely so that the Irwin type bit can have a second cutting lip. Rather than travelling all of the way up the body of the auger, this spiral joints onto the central core of the bit after only a short distance. Waste material that travels up the partial spiral will fall off to one side and end up in the full spiral once they reach the top, before being carried up and out of the bore hole.
An Irwin pattern auger bit with a Jennings pattern tip Additionally, Irwin-pattern auger bits may have Jennings, Scotch or bull nose lips (see below), meaning they can be neat, accurate or hard-wearing, depending on the requirements of the project.
Advantages and disadvantages of Irwin pattern auger bits ADVANTAGES DISADVANTAGES
  • Strong and resilient
  • Made with a variety of guide screws suited to softwood or hardwood.
  • Small risk of deviation due to wood grain or imperfections in stock.

L’Hommedieu

Example of a L'Hommedieu pattern auger, which was developed to make shipbuilding easier by Edgar L'Hommedieu L’Hommedieu auger bits are single twist bits, easily recognised by their lack of a central core.
Close up of the flighting on a L'Hommedieu pattern auger showing the space for waste material This creates a more open flighting that allows for easier evacuation of wood shavings. As a result, L’Hommedieu augers can drill very deep holes without having to be removed part way through the boring process.
The tip of a barefoot auger bit, which has not gimlet point or guide screw L’Hommedieu bits are quite often barefoot – that is, they do not have a guide screw or gimlet point. Their Scotch pattern spurs are capable of guiding the bit reliably through the boring process without imperfections in the wood causing deviations.
Example of a Forstner bit This is similar to the way a Forstner bit cuts through a workpiece.

For more information, see: Forstner BIts

Advantages and disadvantages of L'Hommedieu pattern auger bits ADVANTAGES DISADVANTAGES
  • Barefoot bits do not deviate due to grain or imperfections in stock
  • Sturdy and resilient
  • Difficult to find

Lewis

Example of a Lewis pattern auger bit Lewis pattern auger bits are single twist bits with wide flightings and solid central cores. They resemble a cross between Irwin and L’Hommedieu pattern bits.
An example of an auger bit They are commonly found bits, and popular with DIYers and tradespeople thanks to their durability and resilience.
Advantages and disadvantages of Lewis pattern auger bits

ADVANTAGES

DISADVANTAGES
  • Very easy to find
  • Sturdy and resilient
  • Small risk of deviation due to wood grain or imperfections in stock

Cook

Example of a Cook pattern auger bit Cook pattern bits are double twist bits with upturned wings at their tip.
The tip of a cook pattern auger bit showing the unique shape of the lips The inside of the wings are hollow and sharp, and they act as gouges as the bit spins, making a smooth hole in wood.
In the US, Cook pattern augers are named Gedge pattern augers In the United States, Cook pattern bits are called Gedge pattern bits, as they are named after one of the other inventors who patented the design.
Advantages and disadvantages of Cook pattern auger bits

ADVANTAGES

DISADVANTAGES
  • Gouge-shaped lips bore a very neat hole
  • Reduced risk of tear out
  • Difficult to find

Scotch

Example of a Scotch pattern auger bit The term ‘Scotch pattern’ refers specifically to the spurs of an auger bit. Scotch pattern spurs are part of the web of the auger and the lips slope upwards towards them, meaning that the circumference of the bore hole is cut out after the lips begin to carve out the main part of the bore hole.
An example of an imperfection in a piece of wood - in this case, a knot This can provide a little more stability and accuracy than Jennings pattern spurs, which are more easily thrown off course by the pattern of the grain or imperfections in the wood (such as knots).
Advantages and disadvantages of Scotch pattern auger bits ADVANTAGES
  • Upwards curved lips and spurs mean the bit is unlikely to deviate due to grain or imperfections in stock

Bull nose

Example of a bull nose auger showing a close up of the shape of the tip This unusual auger tip, sometimes referred to as a ‘solid nose auger’, is so named because it resembles a bull’s nose. The two cutting holes in the otherwise solid nose of the auger resemble the nostrils. This is an incredibly resilient tip, as the sharpened lips are an integral part of a thick piece of metal.
Advantages and disadvantages of bull nose auger bits

ADVANTAGES

  • The strongest and most resilient variety of tip