Natural Timber Hardness Ratings: (Janka Rating)
The Janka hardness test simply measures the hardness of timber. It involves measuring the force required to embed a 11mm steel ball into timber to half of it diameter. It is one of the best measurements to determine the ability of timber to withstand denting and wear. It is also a great measurement to understand how hard a species of timber is to saw or nail.
The hardness of timber usually is determined by the direction of the grain. When tested on the surface of the timber it is traditionally known as the "side hardness" of a plank. Testing the cut surface of a piece of timber is known as the "end hardness" which will product very different results. The results are stated in various ways, which can lead to confusion, however in the United States, the measurement is in pounds – force or (lbf). In Sweden it is in kilograms – force or (kgf), and in Australia, either in newtons (N) or kilonewtons (kN). Sometimes results are also treated as units, e.g., "660 Janka".
The following scale is a demonstration of individual species ratings: