types of wood and joints

1. TIMBER

2. TIMBER
Timber:
Wood suitable for building or other engineering purposes
is called timber.
Uses of Timber :
Timber is used for the following categories of works:
1. For Furniture and cabinet making.
2. For light packing cases.
3. For heavy packing cases (for machinery).
4. For making tool handles, toys and turnery articles.
5. For making veneers and plywood.

3. STRUCTURE OF TREE
On examining cross
section of tree it is found
that there is a series of
consecutive rings. These
rings are called annual
rings and each
represents the growth of
one year.
Pith:
It is the first formed portion
of the stem of tree,
around which the annual
rings are formed.

4. STRUCTURE OF TREE
Heart Wood:
Innermost rings surrounding
the pith constitute the
heart wood. This wood is
darker in color, stronger,
more compact and
durable.
Sapwood:
Outer annual rings of the
tree constitute the sap
wood . Compared with
heart wood, sap wood is
lighter in color, weaker and
more liable to decay.

5. STRUCTURE OF TREE
Bark:
It is the outermost protective
covering of cells and
woody fibres on a tree.
Cambium Layer:
Outermost one ring between
the bark and sapwood
which is not yet converted
into wood is known as
cambium layer. In due
course, cambium layer
changes to sapwood.

6. CLASSIFICATION OF TRESS

7. CHARACTERISTICS OF SOFT WOOD AND
HARD WOOD:
Soft woods:
1. It is light in weight and color.
2. Annual rings are very distinct.
3. It is comparatively weaker and spilts easily.
4. It is strong for resisting tensile forces.
5. Its texture is soft and regular.
They are evergreen. Deodar, Chir, pine are the best
examples.

8. CHARACTERISTICS OF SOFT WOOD AND
HARD WOOD:
Hardwood:
1. The wood is comparatively heavier and is darker
in color.
2. The annual rings are not distinct.
3. It is hard and difficult to work upon.
4. It resists shearing stresses.
They include oak, teak, she sham are the best
examples.
They have broad leaves they shed their leaves.

9. COMPARISON OF SOFTWOOD AND
HARDWOOD
* Resin in the most specific use of the term is a hydrocarbon secretion
of many plants, particularly coniferous trees. Resins are valued for their
chemical properties and associated uses, such as the production of
varnishes, adhesives and food glazing agents.

10. CHARACTERISTICS OF GOOD TIMBER
1. It should be from the heart of a sound tree
and be free from sap.
2. It should have straight and close fibres.
3. It should be of uniform color.
4. It should give a clear ringing sound when
struck. Dull heavy sound is a sign of
internal decay.
5. It should have regular annual rings.
6. Timbers with narrow annual rings are
generally the strongest.

11. CHARACTERISTICS OF GOOD TIMBER
7. Freshly cut surface should give sweet smell.
8. It should have bright and smooth surface when
planned. Dull appearance is a sign of defective
timber.
9. Out of same variety of timber, darker and heavier
pieces are stronger.

12. SEASONING:
The purpose of seasoning is to reduce the moisture
content in the wood to a level appropriate to the use
of the objects made from the wood. This prevents
changes in the dimensions and shape of the
objects, eliminates wood rot, increases the strength
of the wood, reduces the weight of the objects,
strengthens glued joints, and improves the quality
of finishing.
Timber contains 70 percent of moisture .the
objects made of wood be deformed whether the
moisture penetrates or absorbed. Therefore
seasoning of wood is done in order to ensure that
they don’t deteriote the object.

13. METHODS OF SEASONING
Natural seasoning
The older method in which the timber is subjected
to controlled temperature, proper aeration is known
as natural seasoning.
Artificial or kiln seasoning: The
environment in which the wood subjected to hot air
blown by us under our control is known as kiln or
artificial seasoning.
Chemical seasoning: We coat a certain
chemical which has low vapour pressure.

14. TIMBER
Wood/timber is destroyed by three agents
 Fire burners: Timber is combustible material. It can
catch fire but cannot catch it by itself. It is inflammable.
We can retard the time of fire by certain chemicals such
as boric and aluminum phosphate which would produce
moisture and retard the fire spreading.
 Fungus: This is a plant which is not capable of
producing. Its food depend on other materials 30 %of
moisture present are favorable for fungus.
 Insect attack:(beetle, wasps, termite) termites are
very important .it is very difficult to control its attack.
heptachloro was used previously to prevent termite.

15. PRESERVATION OF TIMBER:
Methods of preserving:
 Painting: A paint when applied to timber acts not
only as a good preservative but also it enhances
the appearance of the surface so treated.
 Charring: lower ends of the posts that are to be
embedded in the ground are generally charred with
a view to prevent dry rot and attack of worms.
 Tarring:
It consist in coating with tar. Embedded portions of
timber fence posts, ends of door and window
frames are usually tarred.

16. WOOD PRODUCTS
Veneer boards:
 Veneers are those thin sheets of wood that are
peeled off, sliced or sawn from a log of wood
having attractive and artistic arrangement of grains.
Logs of wood are converted into veeners by either
rotary veneer cutters or by veneer slicing machines.
Thickness of these sheets varies from 0.4mm to
6mm. These veneers are glued to inferior timber
surfaces to improve the appearance and to form
decorative and artistic designs.
 Walnut, teak and rose wood are timbers commonly
used for conversion into veneers.

17. WOOD PRODUCTS
Ply wood:
Veneers used for making plywood are
known as piles and plywoods are made by
glueing together piles in odd numbers. It is
one of the most widely used wood products.
It is flexible, inexpensive, workable, re-usable,
and can usually be locally manufactured.
Plywood is used instead of plain wood because
of its resistance to cracking, shrinkage,
splitting, and twisting/warping, and its general
high degree of strength.