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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.

%&amples 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.