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Janka Hardness Scale
Wood Density Information

Janka Hardness: A measure of the hardness of wood, produced by a variation on theBrinellhardness 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 inkilogram-force(kgf), and in Australia, Janka hardness ratings are either innewtons(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 hardness 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.

  • Ipe3680 (approx. 3 times harder than Oak).
  • Cumaru3540
  • Massaranduba3190
  • Angelim Pedra3040
  • Tigerwood2620
  • Jatoba2350
  • Garapa2280
  • Batu2100
  • Purple Heart1860
  • Black Locust Decking (U.S.)1700
  • Red Oak1290
  • Keruing1270(truck decking).
  • Teak1155
  • Honduran Mahogany900
  • Mahogany800
  • Dark Red Meranti780
  • Southern Yellow Pine680
  • Douglas Fir660
  • Spanish Cedar600
  • Alaskan Yellow Cedar580
  • Cypress460
  • Western Red Cedar350

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Deck Builders USA
339 S Atlanta Street, Roswell GA 30075
Call: 770-587-3325