Drilling resistance measuring device for the professional inspection of trees and wood

With a drilling resistance measuring device like the IML-RESI PowerDrill® the internal structure of trees and woods can be inspected in an uncomplicated and gentle way. Rotten spots as well as hollow spaces and other defects in the wood can be detected reliably without damaging the wood over a large area.

Functionality of the drilling resistance measuring device

The drilling resistance measuring device contains a long and thin drilling needle that drills into the wood. The drilling resistance measuring device measures the torsional moment of the motor in relation to the penetration depth of the drilling needle. The torsional moment results from the friction of the needle shaft in the wood and the chipping at the tip of the needle. However, for a clear determination of the shaft friction, the drilling needle must drill into a hollow space or pierce the entire trunk and emerge from the wood at the end. 

For a higher accuracy and a better identification of decay, the IML-RESI PowerDrill® measures the feed force of the drilling needle at its tip in addition to the drilling resistance. In this way, the IML-RESI wood testing system determines the relative density distribution of woods. By means of changes in the relative density, hollow spaces in the wood and other damages can be detected.

Condition of the drilling needle

The drilling needle made of steel has a special alloy and surface coating as well as a reinforcement of the needle tip, which gives the drilling needle a special stability. The diameter of the needle shaft is only 1.5 mm, whereas the diameter of the needle tip measures 3.0 mm. The damage to the wood caused by the drilling is kept to a minimum. As a rule, 100 to 150 drillings per needle are possible, depending on the application. In addition, a special drilling needle is available for the drilling resistance measuring device, which is to be used exclusively for drilling holes in wooden poles.

Replacing the drilling needle

The IML-RESI PowerDrill® optionally checks the needle diameter after each measurement. If the needle is too worn, it should be replaced, otherwise the measuring result will be too inaccurate and it may lead to overstraining the measuring device. The “Automatic drilling needle change” program guides the user through the changing process.

Operation via the integrated display

Via the display, integrated in the drilling resistance measuring device, the user can make settings and view the results of the current and all stored measurements. One important setting option, for example, is to adapt the feed speed to the type of wood to be controlled. The user can adjust this infinitely variable from 15 to 200 cm/min. Furthermore, the IML-RESI PowerDrill® provides the possibility to safe individual remarks on the measurements.

Performance of the drilling resistance measurement

Depending on the measured object, several drillings in different positions are necessary. 

The display on the drilling resistance measuring device then shows the result. It is important that the correct feed speed is set by the operator and adapted to the hardness of the wood, so that a significant measurement result is shown.

Illustration of the measurement results

The user receives the measurement result in the form of a drilling curve, in which the drilling resistance and the feed force are displayed as measuring curves. In some cases it is recommended to drill an additional reference hole. In the case of wooden poles, it is even possible to automatically evaluate the measurement curve. Individual thresholds can be programmed for evaluation.

The user receives the measurement result in the form of a drilling curve, in which the drilling resistance and the feed force are displayed as measuring curves. In some cases it is recommended to drill an additional reference hole. In the case of wooden poles, it is even possible to automatically evaluate the measurement curve. Individual thresholds can be programmed for evaluation.

The device stores the measurement results, which can also be transferred to a computer via a USB or Bluetooth interface and then evaluated in detail with the appropriate software. It is also possible to print out the measurement curve locally using a special portable printer.

Evaluation of the measurement results using software

With the help of the PD-Tools software, the user can also define his own criteria when analysing the measurement results, which he wants to use for his evaluation of the wood health. Different sections of the curve can be highlighted in different colors, making it easier to interpret the measurement results. The user can also view and compare the results of different measurements at the same time. Hollow spaces and other internal defects in the wood can be clearly identified by looking at flattened areas in the measurement curve.

When evaluating the wood quality, the user has to consider the local conditions and tree ring width in addition to the wood species, as these can influence the wood quality. Experienced specialists can see from the measurement curve which internal defect is present in the wood. For example, they can differentiate between decayed areas and fissures.

Advantages of the drilling resistance measurement

The drilling resistance measurement allows an immediate analysis at the location of the measurement and a fast evaluation of the results. This allows the user to evaluate the stability and wood condition of the tree or wood to be checked immediately after the measurement. To be able to do this reliably, however, professional training and adequate experience are necessary.

A further advantage of the drilling resistance measurement is that it is possible to check the wood in the critical area below ground level without having to excavate the wood. After all, it is precisely in this area that the conditions are ideal for wood decay by fungus.

Disadvantages of the drilling resistance measurement

When measuring the drilling resistance of trees, minor injuries occur. However, the drill holes are automatically closed again by the remaining wood particles and the wood does not lose stability. Furthermore, the measurement only reflects the condition in the selected drilling area, so this should be carefully evaluated by trained and experienced specialists.

Fields of application of the drilling resistance measuring device

The IML-RESI PowerDrill® is suitable for measurements on living trees and construction wood and is used in the following areas:

The IML-RESI wood inspection system is used to detect hollow spaces and fissures that are not visible from the outside. In addition, it can be used to detect decay in different stages of progress as well as growth of annual rings. Furthermore, the drilling resistance measuring instrument supports the evaluation of wood quality and stability with significant measurement results. The measures based on these results can prevent serious personal injury and material damage caused by falling trees or collapsing wooden structures in time. The IML-RESI PowerDrill® is designed for tree inspection within the scope of the obligation to maintain safety on the traffic.


Leave a Reply

Your email address will not be published. Required fields are marked *