Dry Wood Borer Tutorial Page

A Tutorial for Using the Dry Wood Borer

First, place the guide plate in the desired position, and fasten it to the log with two wood screws. I've found, however, that simply holding the guide plate up with one hand and firmly grasping the plate with your fingers works quite well (Figure 1) and prevents two additional holes from being drilled. Be extremely careful, however.

Figure 1. Holding the guide plate up to start the drill tip.

Next, slowly start your variable speed drill so that it is lightly cutting the wood (Figure 2). Slowly increase its speed until the drill has penetrated about 0.25-0.5 inches (8-12 mm). The guide plate should now be removed.

Figure 2. Using the dry wood borer with an electric drill.

To ensure you have the outermost ring when finished, place a black dot on the core surface with a Sharpie (Figure 3).

Figure 3. Notice the black dot that will help locate the surface.

Every 0.5 inches (12 mm), extract the drill bit partially several times after decreasing the speed of the drill bit to allow the sawdust to fall out of the hole (Figure 4). Alternatively, extract the drill bit and have an assistant use a can of compressed air to blow out the sawdust. Once the desired depth is reached, extract the drill bit and blow out any additional remaining sawdust. You should always extract the drill bit while it is still turning after decreasing its rotation speed. Do not try to extract the drill bit from the beam of wood when the drill bit is stopped completely. This will break the core.

Figure 4. Every so often, extract the drill bit partially to allow
the sawdust to fall out while drilling.

Insert the extractor along one side of the core until it will go no further. Turn the extractor to cut the core. Repeat in several locations around the core if necessary. Depending on the wood, you may hear an audible break (as with oak, for example). Carefully pull the extractor from the hole and the core should follow (Figure 5).

Figure 5. Extracting the core.

Once extracted, the core should be firmly glued to a wooden core mount. Because these cores often are already dry, they do not require additional drying time and can be mounted immediately after extraction with wood glue or Elmer's glue and fastened simply with masking tape (Figure 6).

Figure 6. Note how the core has been mounted on the wooden
core mount with Elmer's glue and masking tape.

At the Laboratory of Tree-Ring Science, we place a 5/8ths inch (14 mm) cork firmly in the hole, and then paint the hole with water-insoluble oil-based paints to hide the hole and the cork (Figure 7).

Figure 7. Painting the cork with custom-designed oil paints.