Riving knife (tool)
A riving knife or driving wedge is a wedge- shaped tool , which in the forestry for felling trees and chipless cutting of tree trunks , large wood pieces, blocks of stone is used.
Riving knife are made of different materials and in different sizes and designs. The wedge angle is usually between 10 and 25 degrees, with or without beveling the cutting edge, the length between 15 and 30 cm and the weight between a few hundred grams and a few kilograms .
Splitting wedges are traditionally made from solid steel . For newer versions also are aluminum alloys and plastics used. The wedge surfaces can be provided with shallow grooves , grooves or ridges in order to improve guidance and also to reduce friction . Some models made of softer materials are hollow. They are being fitted with hardwood wedge with a round shank used and attached aluminum ring (brass knuckles).
Felling and splitting wood
Depending on the application, a distinction can be made between log wedge (for splitting logs and blocks) cutting wedge and felling wedge . The cutting wedge is driven into the fall cut when felling and ensures that the weight of the tree does not press on the rail of the chainsaw and pinch it. The felling wedge pushes the tree in the direction of fall when it hits the cut. Felling and cutting wedges are usually made of plastic or aluminum in order not to damage the chainsaw chain when felling.
In many cases, the felling wedge at small tree diameters is formed by a so-called breaking bar replaced (a lever-like tool) or the tree drawn with a rope in the direction of fall.
When doing forest work, it should be noted that driving steel wedges with a steel hammer is prohibited in the accident prevention regulation "Forests" (§ 3) due to the risk of steel particles flying around (jumping off the wedge). There are also wedges that mechanically lever the tree over a gear.
When splitting , the wedge is driven into the block along the fiber direction. A wedge made of iron is usually used for this, as it is easier to drive into the wood. Several manufacturers also offer rotating splitting wedges to make splitting easier. Since this work is very exhausting, a log splitter is mostly used nowadays .
The wedges with a large sledgehammer driven or maul. The wooden insert made of ash or hickory serves to reduce wear on iron and aluminum wedges. With solid iron wedges, the additional purchase of a wooden sledge hammer is avoided.
A special form is provided with a handle provided Maul , which can be used with his back as a normal sledgehammer. The fin is wedge-shaped with a sharpened edge, similar to an ax , and can be used to split pieces of wood directly.
Stone breaking
Splitting wedges made of steel alloys were and are used as stone splitting tools for the extraction of rocks . The wedge is guided between two pieces of lining in order to use the better sliding friction between steel surfaces and to avoid sliding on the stone surface. First the pieces of food are inserted and then driven apart with the wedge. This two-part form is available commercially under the designation drive wedges.
Today this tool is less and less used in the stonemason's handicrafts area for the processing of natural stones , but it is still used in the quarry . In paleontology , geology and hobbyists such tools are widely used for brick breaking.
