BORERHANDLING

Dendrochronological core drill: Handling-instructions

The core drill is the result of a profound test series and was specially developed for dendrochronological purposes. It is manufactured in Germany and consists of
HSS-steel (High-Speed-Steel). The different components of the borer are hardened depending on their area of application.

Our tool is equipped with a drive arbor for 13mm drill chucks (the long version needs a 16mm key-type drill chuck). As an electric drill suitable for dendrochronological purposes we would recommend the Metabo BE 622 S- R+L or comparable machines. With its max. ca. 600 rpm and 620W this machine holds an ideal rate of rotation and appropriate power available. It is for these technical data that this machine can be often found in carpenters’ workshops. Because of its high torsional force the drill must be used only with the additional handhold (within the scope of supply).

Please take care that your drill still has a functioning drive arbor. You will get the best results with key-type drill chucks, which can easily be re-stressed. Older drive arbors often have worn-out chuck jaws which are no longer able to hold the core drill sufficiently. Result: The borer slips through the drive arbor. As an additional effect due to worn-out chuck jaws, imbalances may occur, which negatively affect the concentricity of the core drill. Therefore the exchange of the drive arbor every once in a while should be as natural as the re-sharpening of the core drill itself.

Notice: The tool can only be used with the assistance of a fence (special tool, within the scope of supply)!

Drilling on the object under investigation should only be done with moderate pressure. Pay attention to the ejection of the borings. The borings should be ejected constantly and uniformly. If the ejection should be interrupted while drilling, the core drill must partly be pulled out of the borehole and afterwards carefully lead in again. Doing this will eject compressed borings from the borehole. Especially in case of wood with high moisture-contents the borings often agglutinate.

The thread of the borer must never be treated with oil. In case of sluggishness it has to be treated with a wire brush first. Afterwards it can be maintained with graphite or a copper paste (for example OKS 240, commercially available) to regain the ease of motion. Do not adjust the thread by using wrenches; adjustment by hand is totally sufficient. If both parts of the tool have to be separated from each other, work can be done with two open-end wrenches of 17 mm.

If the sample should be broken and it/ or parts of it should be stuck within the drill, we recommend to separate the core-drill from its thread using the 19 mm open end wrenches. Afterwards the sample may be pushed out carefully by using the 10mm round-steel stick (within the scope of supply). The core should be pushed out in direction of the thread. If pushed in direction of the drill bit, the sample might become even more stuck or may be damaged because of an offset about 15 mm underneath the drill bit.

Too much heat generation does harm to the core drill and in the worst case deteriorates the hardening of the steel. To avoid this, work should be interrupted if too much heat generation occurs so that the tool may cool down. Under normal conditions overheating should never occur, but might happen if the drill bits sharpening has perished and propulsion has to be gained by applying more and more pressure to the tool. Normally moderate pressure is sufficient for the propulsion of the core drill. If much force is needed for propulsion this indicates that the drill should be re-sharpened soon.
If the drill bits become tarnished in a blueish colour, this indicates the need for re-sharpening too. Referring to the experiences made so far, a hundred of drillings may be done before a re-sharpening is needed.