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Janka Hardness Scale

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Janka Hardness Scale

Postby James Tonguet » Wed Sep 05, 2012 9:26 am

For those who were curious ...


Janka Hardness Scale
Janka hardness measurements reflect the number of pounds pressure it takes to press a .444" diameter steel ball, to it's maximum diameter, into a vertical sawn section of wood.


Wood Variety sorted by Hardness
Macassar Ebony 3220
Screwbean Mesquite 2335
Persimmon 2300
Dogwood 2150
Ohia 2090
Osage-Orange 2040
Hop Hornbeam 1860
Pecan 1820
Shagbark Hickory 1820
Hornbeam 1780
Apple 1730
Almond 1700
Black Locust 1700
Honey Locust 1580
Witch Hazel 1530
Orientalwood 1480
Bastogne Walnut 1460
Madrone 1460
Rosewood 1450
Sugar Maple 1450
Cuban Mahogany 1430
Tanoak 1400
African Mahogany 1350
White Ash 1320
Beech 1300
Myrtlewood 1270
Yellow Birch 1260
English Walnut 1200
Green Ash 1200
Pacific Yew 1150
Koa 1110
Cascara 1040
Southern Magnolia 1020
American Black Walnut 1010
Claro Walnut 950
Black Cherry 950
Imbuya 950
Sourwood 940
Eastern Red Cedar 900
Hackberry 880
Longleaf Pine 875
Rock Elm 860
Slippery Elm 860
Bigleaf Maple 850
Black Ash 850
Tropical American Mahogany 845
American Elm 830
Western Larch 830
Red Lauan 825
Sycamore 770
Port Orford Cedar 720
Silver Maple 700
White Lauan 690
Douglas Fir 685
Sassafras 630
Tamarack 590
Northern Catalpa 550
American Chestnut 540
Yellow Poplar 540
Sitka Spruce 510
Bald Cypress 510
Butternut 490
Redwood 480
Black Willow 420
Basswood 410
Yellow Buckeye 350
Western Redcedar 360
Aspen 350
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Re: Janka Hardness Scale

Postby David King » Wed Sep 05, 2012 11:28 am

James,
Are these figure from tests that you conducted personally?
There are some notoriously misleading Janka figures out on the web so it's always nice to know when better data comes to the fore.

That eastern red cedar figure looks suspiciously high to me for instance.
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Re: Janka Hardness Scale

Postby Alan Peterson » Wed Sep 05, 2012 2:58 pm

Mr Janka must have been a very interesting guy to live next door to. Every recycling day, the bin out by his curb would have been filled with wood fragments shot through with ball bearings.

Wonder if one of his neighbors was Mr Scoville, the pepper dude?
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Re: Janka Hardness Scale

Postby James Tonguet » Thu Sep 06, 2012 11:49 am

The list is from Oregon Wild Woods site , and I'd agree there are some discrepencies , not even accounting for natural variances.
Like most generalites it is only a baseline
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Re: Janka Hardness Scale

Postby David King » Thu Sep 06, 2012 12:13 pm

When they say a "vertical sawn section of wood" do they mean end-grain compression or the quarter-sawn face?
I'd rather look at a comparison of woods with multiple attributes such as density, modulus of elasticity and Janka to see where some species diverge from the norm.
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Re: Janka Hardness Scale

Postby James Tonguet » Thu Sep 06, 2012 4:21 pm

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 is done in accordance with ASTM D 1037-7 testing methods. Lumber stocks tested ranges from 1" to 2" thick. Resulting Janka Hardness Numbers are an average. There is a standard deviation associated with each species, but these numbers are not given. It is important to note no testing is done on flooring. Other factors affect how flooring performs: type of core for engineered flooring such as pine, HDF, poplar, oak, birch; grain direction and thickness; floor or top wear surface. The chart is not to be considered an absolute; it is meant to help people understand which woods are harder than others.
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Re: Janka Hardness Scale

Postby David King » Thu Sep 06, 2012 7:36 pm

If I'm reading that correctly "side hardness" is equivalent to testing the outside of a flat-sawn plank?
I take it .444" is pretty close to 10mm?
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Re: Janka Hardness Scale

Postby Mario Proulx » Fri Sep 07, 2012 1:52 am

f I'm reading that correctly "side hardness" is equivalent to testing the outside of a flat-sawn plank?
I take it .444" is pretty close to 10mm?


Yup, it's pretty-well useless dribble for luthiers, unless we plan on building instruments that high heel-wearing women will dance upon....
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Re: Janka Hardness Scale

Postby Clay Schaeffer » Fri Sep 07, 2012 9:46 am

Flamenco masoquista ? <g>
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Re: Janka Hardness Scale

Postby Dennis Duross » Sat Sep 08, 2012 9:53 am

I would think the most useful information the Janka scale could provide us with would be the suitability of a given wood for use as a fingerboard.
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Re: Janka Hardness Scale

Postby David Malicky » Sat Sep 08, 2012 2:59 pm

For very oily woods, I've wondered if the Janka test might not be a great indicator of the "knife edge" hardness. I've tried using Lignum Vitae for nuts and saddles and find it dents somewhat easily, despite getting a Janka score of 4500.
http://en.wikipedia.org/wiki/Janka_hardness_test
The high oil content would give it a high Poisson's ratio, which would give good resistance to a large steel ball or a ship propeller shaft (the oil takes up the usual air space, making the wood less compressible). But oil wouldn't resist a highly concentrated force like a string.
Lignum Vitae also lasercuts very easily, while Ebony (with a lower Janka) is almost impossible to lasercut, and makes a harder nut/saddle.
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Re: Janka Hardness Scale

Postby David King » Sat Sep 08, 2012 4:35 pm

David
That's an interesting observation. Have you played around with African Blackwood? I find it much harder than the ebonies in my collection and virtually impossible to dent or mar with a thumbnail. It's a very resinous wood and it has a tendency to melt when it gets too hot.
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Re: Janka Hardness Scale

Postby Darrel Friesen » Sun Sep 09, 2012 6:31 pm

That would be the same thing I have experienced David. African Blackwood has been the hardest most difficult wood I've worked with. Rasps and abrasives work best for me. I find it a bear to carve with hand tools, but can be done with patience.
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Re: Janka Hardness Scale

Postby David King » Sun Sep 09, 2012 9:04 pm

ABW actually machines beautifully, on the lathe the swarf comes off in a continuous string. On the mill the machined surfaces are glossy.
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Re: Janka Hardness Scale

Postby David Malicky » Thu Sep 13, 2012 2:11 am

I've never tried ABW, but from those comments I'm looking forward to trying it for some saddles -- thanks!
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Re: Janka Hardness Scale

Postby David King » Thu Sep 13, 2012 10:16 pm

David,
I've done plenty of electric guitar (strat) bridges and saddles from ABW. They hold up well apparently.
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