To design and machine a customized increment borer that could effectively sample hardwood and softwood trees greater than three feet in diameter. This project required hundreds of hours of work related to the creation of 3D models in SolidWorks, G-code via Autodesk HSMWorks, and the use a Haas CNC lathe and vertical mill with a 5-axis rotary. Background work involved research on current and previous borer designs, properties of available materials, and geometrical configurations.

An increment borer is a hollow auger typically made out of A2 tool steel with tapered cutting threads on one end that screw into the wood of a living tree and remove a long, thin dowel of wood contained within the shaft. The device is operated by hand using a handle that attaches to the opposing end. Its purpose is to sample trees in a minimally invasive way by coring out a wood sample while compressing the wood around it via radial protrusions known as spreader bars. Compressing the wood around the shaft is necessary to prevent wood fibers from springing back onto the shaft and locking the borer in place. Depending on the design, these spreader bars lie either just behind the threads (Haglöf design) or on the roots of the threads (Djos and Suunto designs). Increment borers are sold with either double- or triple-start threads, the latter traveling farther into the tree per rotation while also requiring more torque to turn. The number of spreads bars spaced evenly around the shaft will always equal the number of start threads.

There are several design problems with the increment borers available today. The first problem occurs with Haglöf borers greater than ~16–18″ in length, which are at risk for becoming stuck in the tree when a pocket of rotted wood or cavity comes into contact with the threads. The borer ends up spinning in place and requires significant backwards pressure to re-engage the threads that are being impeded by the spreader bars as they rub against the wood behind them. The Djos and Suunto designs aim to solve this issue but do not perform as well when it comes to compressing the wood. This is due to the fact that the spreader bars are situated between the tapered cutting threads, meaning they protrude above the diameter of the shaft to a lesser degree. The total length of these borers is limited to 16″ and require more advanced machining methods to produce than Haglöf borers. Both the Djos and Haglöf designs lack sufficiently wide conical cutting tips at the end of the threads that provide greater accessibility for sharpening and maintenance.