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
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.
The flighting on Russell Jennings augers is double-twisted, meaning the bit bores a neat hole.
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
DISADVANTAGES
Bores a neat, clean hole
Small risk of deviation due to wood grain or imperfections in stock.
Irwin
Irwin-pattern augers, also known as solid core augers, are single twist tools. Some have a unique extra half-spiral at their tip.
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.
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
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
L’Hommedieu auger bits are single twist bits, easily recognised by their lack of a central core.
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.
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.
This is similar to the way a Forstner bit cuts through a workpiece.
For more information, see: Forstner BIts
ADVANTAGES
DISADVANTAGES
Barefoot bits do not deviate due to grain or imperfections in stock
Sturdy and resilient
Difficult to find
Lewis
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.
They are commonly found bits, and popular with DIYers and tradespeople thanks to their durability and resilience.
ADVANTAGES
DISADVANTAGES
Very easy to find
Sturdy and resilient
Small risk of deviation due to wood grain or imperfections in stock
Cook
Cook pattern bits are double twist bits with upturned wings at their tip.
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 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
DISADVANTAGES
Gouge-shaped lips bore a very neat hole
Reduced risk of tear out
Difficult to find
Scotch
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.
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
Upwards curved lips and spurs mean the bit is unlikely to deviate due to grain or imperfections in stock
Bull nose
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.