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The Janka hardness test (; ), created by Austrian-born American researcher Gabriel Janka (1864–1932), measures the resistance of a sample of wood to denting and wear. It measures the force required to embed an steel ball halfway into a sample of wood. (The diameter was chosen to produce a circle with an area of 100 square millimeters, or one square centimeter.)
A common use of Janka hardness ratings is to determine whether a species is suitable for use as flooring. For hardwood flooring, the test usually requires an sample with a thickness of at least 6–8 mm, and the most commonly used test is the ASTM D1037. When testing wood in lumber form, the Janka test is always carried out on wood from the tree trunk (known as the heartwood), and the standard sample (according to ASTM D143) is at 12% moisture content and clear of knots.
The hardness of wood varies with the direction of the wood grain. Testing on the surface of a plank, perpendicular to the grain, is said to be of "side hardness". Testing the cut surface of a stump is called a test of "end hardness". Side hardness may be further divided into "radial hardness" and "tangential hardness", although the differences are minor and often neglected.
The results are stated in various ways, leading to confusion, especially when the actual units employed are often not attached. The resulting measure is always one of
Janka Hardness Scale For Wood – Side Hardness Chart of Some Woods
USDA – Wood Handbook – Wood as an Engineering Material
USDA – Janka Hardness Using Nonstandard Specimens
{{DEFAULTSORT:Janka Hardness Test Woodworking Woodcarving Wood Hardness tests
The Janka hardness test (; ), created by Austrian-born American researcher Gabriel Janka (1864–1932), measures the resistance of a sample of wood to denting and wear. It measures the force required to embed an steel ball halfway into a sample of wood. (The diameter was chosen to produce a circle with an area of 100 square millimeters, or one square centimeter.)
A common use of Janka hardness ratings is to determine whether a species is suitable for use as flooring. For hardwood flooring, the test usually requires an sample with a thickness of at least 6–8 mm, and the most commonly used test is the ASTM D1037. When testing wood in lumber form, the Janka test is always carried out on wood from the tree trunk (known as the heartwood), and the standard sample (according to ASTM D143) is at 12% moisture content and clear of knots.
The hardness of wood varies with the direction of the wood grain. Testing on the surface of a plank, perpendicular to the grain, is said to be of "side hardness". Testing the cut surface of a stump is called a test of "end hardness". Side hardness may be further divided into "radial hardness" and "tangential hardness", although the differences are minor and often neglected.
The results are stated in various ways, leading to confusion, especially when the actual units employed are often not attached. The resulting measure is always one of force
In physics, a force is an influence that can cause an Physical object, object to change its velocity unless counterbalanced by other forces. In mechanics, force makes ideas like 'pushing' or 'pulling' mathematically precise. Because the Magnitu ...
. In the United States, the measurement is in pounds-force (lbf). In Sweden, it is in kilograms-force (kgf), and in Australia
Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
, either in newtons (N) or kilonewtons (kN). This confusion is greatest when the results are treated as units, for example "660 Janka".
The Janka hardness test results tabulated below followed ASTM
ASTM International, formerly known as American Society for Testing and Materials, is a standards organization that develops and publishes voluntary consensus technical international standards for a wide range of materials, products, systems and s ...
D 1037-12 testing methods. Lumber stocks tested range from 1" to 2" (25–50 mm) thick. The tabulated Janka hardness numbers are an average. There is a standard deviation associated with each species, but these values are not given. No testing was done on actual flooring.
Other factors affect how flooring performs: the type of core for engineered floorings, such as pine, HDF, poplar, oak, or birch; grain direction and thickness; floor or top wear surface, etc. The chart is not to be considered an absolute; it is meant to help people understand which woods are harder than others.
Typical Janka hardness values
References
External links
Janka Hardness Scale For Wood – Side Hardness Chart of Some Woods
USDA – Wood Handbook – Wood as an Engineering Material
USDA – Janka Hardness Using Nonstandard Specimens
{{DEFAULTSORT:Janka Hardness Test Woodworking Woodcarving Wood Hardness tests