Auger bits come in various designs, but they all excel at one thing. Making a clean hole in timber quickly . Here we have three common types:
- Left – Russell Jennings type auger
- Center – Irwin type auger
- Right – Cook type auger
The Jennings and Irwin are similar in cutting action and both have a screw tip (lead screw) to drive the bit into the work. They also have cutting spurs to prevent tearout. The actual cutting is done by two beveled edges between the spurs and tip. The difference is in manufacturing methods. The Jennings starts as a flat bar and is twisted into shape, whereas the Irwin types have a central shaft with one twist. The Cook type auger differs in that it’s tips are bent back. This ensures a smooth cut. I find these work best in blind holes.
In practice these bits are very easy to use well. It takes very little force to do the work as the lead screw pulls the bit into the work piece, the spurs cut the hole and the cutting edges remove the waste. Use a suitably sized brace to drive the bit, they come in various sizes, with 10 – 12 inch sweeps being common. A 10 inch sweep brace and set of auger bits. (Brace & bits) Auger bits like these are still available today, however they were most commonly made in these designs from around 1850 to the end of WW2.