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What is an Increment Borer?

Jacob Queen
Jacob Queen

An increment borer is a tool used by people who are studying forests or trying to diagnose various problems with trees. They are designed to drill into the wood and extract a very thin sample, which can be studied to show the tree's history and condition. The main idea behind an increment borer is to get the sample without damaging the tree, and for this reason, the sample is generally very thin. Increment borers consist of a long, hollow drill bit with a hole at the end, a cross handle that gives good leverage when turning with two hands, and an extractor for pulling out the sample.

When using an increment borer, the forester will generally have to lean into the handle with his weight to get it started into the wood, although this can vary depending on the strength of the tree being tested. Once the borer penetrates the wood, the threads will do most of the work of pulling the device into the tree, and all the forester has to do is continue turning. The general goal is to bury the borer about halfway into the tree, or slightly beyond that, and this can often be done in a minute or less.


Once the device is deep enough, the extractor, which is basically a piece of metal for the sample to rest on, is inserted from the outside. At this point, the forester will generally turn the increment borer in the opposite direction to break off the sample, and then pull out the extractor. Sometimes the samples may be broken into separate pieces, depending on the strength and condition of the wood.

In some cases, the samples may be stored in test tubes or even drinking straws. After that, they are often labeled with the location and species of the tree along with other important information, depending on the purpose of the researchers. In some cases, an increment borer might be used to sample a single tree, and in other cases, researchers sample multiple trees in a given area to determine their age, history, or if they have various diseases.

The size of an increment borer can vary significantly depending on the species and age of the trees being sampled. For example, it could be dangerous to use a large increment borer on a juvenile tree, and a small borer wouldn’t be able to penetrate deep enough into a larger tree. There are also variations in the design of the drill bits used because some trees are more difficult to penetrate.

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