hardwood species

JANKA HARDNESS TEST

Patagonian Rosewood
Ipe
Cumaru
Brazilian Redwood
Spotted Gum
Brazilian Cherry / Jatoba
Kekatong
Santos Mahogany
Sucupira
Merbau
Jarrah
Goncalo Alves
Hickory / Pecan, Satinwood
Afzelia / Doussie
Bangkirai
Kempas
Highland Beech
Wenge
Sapele
Natural Bamboo
Australian Cypress
White Oak
Tasmanian Oak
Ash (White)
American Beech
Red Oak (Northern)
Yellow Birch, Iroko
Carbonized Bamboo
Teak
Siberian Larch
Black Walnut/North American Walnut
Teak
Black Cherry, Imbuia
Hevea
Paper Birch
Lacewood
Douglas Fir
Alder (Red)
Larch
Eastern White Pine
3840
3540
3190
2473
2350
2340
2200
2140
1925
1910
1850
1820
1810
1798
1710
1686
1630
1510
1380
1375
1360
1350
1320
1300
1290
1260
1180
1155
1100
1010
1000
950
930
910
840
660
590
590
380

A measure of the hardness of wood, produced by a variation on the Brinell hardness test. The test measures the force required to push a steel ball with a diameter of 11.28 millimeters (0.444 inches) into the wood to a depth of half the ball’s diameter (the diameter was chosen to produce a circle with an area of 100 square millimeters). In Janka’s original test, the results were expressed in units of pressure, but when the ASTM standardized the test (tentative issue in 1922, standard first formally adopted in 1927), it called for results in units of force.

The results are stated in various ways in different countries, which can lead to confusion, especially since the name of the actual unit employed is often not attached. In the United States, the measurement is in pounds-force. In Sweden it is apparently in kilogram-force (kgf), and in Australia, Janka hardness ratings are either in newtons (N) or kilonewtons (kN). Sometimes the results are treated as units, e.g., “360 janka.”

The hardness of wood usually varies with the direction of the grain. If testing is done on the surface of a plank, with the force exerted perpendicular to the grain, the test is said to be of “side hardness.” Side hardnesses of a block of wood measured in the direction of the tree’s center (radially), and on a tangent to the tree’s rings (tangentially), are typically very similar. End testing is also sometimes done (that is, testing the cut surface of a stump would be a test of end hardness). The side hardness of teak, for example, is in the range 3730 to 4800 newtons, while the end hardness is in the range 4150 to 4500 newtons.

 The most common use of Janka hardness ratings is to determine whether a species is suitable for use as flooring.

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