Janka hardness test
The Janka hardness test measures the resistance of a type of wood to withstand denting and wear. It measures the force required to embed an 11.28 mm (0.444 in) steel ball into wood to half the ball's diameter. This method leaves an indentation. A common use of Janka hardness ratings is to determine whether a species is suitable for use as flooring.
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."
The results are stated in various ways, which can lead to confusion, especially when the name of the actual units employed is often not attached. In the United States, the measurement is in pounds-force (lbf). In Sweden it is in kilograms-force (kgf), and in Australia, either in newtons (N) or kilonewtons (kN). Sometimes the results are treated as units, for example "660 Janka".
To convert pound-force (lbf) units to newtons N multiply pound-force by 0.45359237 then multiply by 9.80665 (1 standard g in units of m/s2). Janka hardness N = (lbf × 0.45359237) × 9.80665 OR multiply by 4.4482216152605. To get lbf from N, multiply N by 0.224808943099736.
The Janka Hardness test below is done in accordance with ASTM D 1037-7 testing methods. Material stocks ranges from 1" to 2" thick. (Numbers are an average. Testing is done on samples, not flooring that is already in place.) There is a standard deviation, but these numbers are not published. Other factors affect how flooring performs: type of core (for engineered flooring), grain direction and thickness floor or top wear surface.
[edit] References
- ^ a b Johnny W. Morlan. "Wood Species Janka Hardness Scale/Chart By Common/Trade Name A - J". The World's Top 125 Known Softest/Hardest Woods. http://www.morlanwoodgifts.com/MM011.ASP?pageno=207. Retrieved 20 December 2011.
- ^ "Bamboo Flooring". EcoTimber Flooring. http://www.ecotimber.com/guide/ecofriendly-bamboo-flooring.html.
[edit] External links
- Janka Hardness Scale For Wood Flooring Species
- Janka Hardness Scale For Wood - Side Hardness Chart of Some Woods
- The World's Top 125 Known Softest/Hardest Woods
- USDA - Wood Handbook - Wood as an Engineering Material
- USDA - Janka Hardness Using Nonstandard Specimens
- Janka Hardness Scale For Hardwood Flooring
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