Post on 11-Feb-2018
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3.1.1 Hardness
If a block of wood is struck with a hammer when lying on a bench, the hammer-head will
make a dent in the wood, which will be deeper or shallower according as the wood is soft
or hard. A wood is said to be very hard when it requires a pressure of about 3,000 pounds
per square inch to make an impression one-twentieth of an inch deep.
-A hard wood requires only about ,!00 pounds to produce the same effect.
-"airly hard wood will be indented by a pressure of #,!00 pounds.-$oft woods require even less.
%&les of wood based on their hardness are as follow'
Very hard wood' (ak, )aple, %lm
Hard wood' Ash, *herry, +irch
Diagram 3.1 1 Oak tree.
Diagram 3.1 2 Sugar maple tree.
Diagram 3.1 3 Elm tree.
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Soft wood' emlock, ed wood, oplar
3.1.2 Toughness
Diagram 3.1 !herry tree.Diagram 3.1 " #sh tree.
Diagram 3.1 $ %ir&h tree.
Diagram 3.1 ' (oplar treeDiagram 3.1 ) *ed wood
Diagram 3.1 + Hemlo&k tree
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/oughness/ is a word which is often used in relation to timber, and implies both strength
and pliability, such as is found in the wood of the elm and the hickory. $uch timber will
withstand the effect of 1ars and shocks which would cause other woods like pine to be
shattered."or the purpose of this schedule, the simplified classifications ,2low, -
2medium and H2high have been adopted.