Timber

TIMBER
TYPES OF TREES FROM TIMBER PRODUCTION
STRUCTURE OF A TREE
PROCESSING OF TIMBER

1. PREPARED
BY
ER. SANJEEV SINGH
[email protected]

2. CONTENT
•TIMBER
•TYPES OF TREES FROM TIMBER PRODUCTION
•STRUCTURE OF A TREE
•PROCESSING OF TIMBER

3. TIMBER
•Woodisoneofthemostusednaturalbuildingmaterialsintheworld.
Anumberofvaluablepropertiessuchaslowheatconductivity,small
bulkdensity,relativelyhighstrength,amenabilitytomechanical
workingetc.makeswoodasfamousbuildingmaterial.
•Timbercanbeusedinmosteconomicalwaywithoutwastinganyof
thederivativeofit.Eventhesawdustobtainedduringwoodsawing
canalsobeusedtomakefiberboards,paperetc.

4. TYPES OF TREES FOR TIMBER
PRODUCTION
1.Exogenous
•Exogenoustreesareoutwardgrowingtrees.Horizontalsectionofsuchtree
containsseveralringswhicharenothingbutannualrings.Theseringscan
beusedtopredicttheageoftree.Mostoftheexogenoustreesareusefulfor
manyengineeringpurposes.
•Exogenoustreesaresubclassifiedintofollowingtypes.
•Conifers
•Deciduous

5. CONIFERS
•Conifersarenothingbutsoftwoodproducingtreeswhicharealso
calledasevergreentrees.Thetimberofthesetreesislightcolored,
lightinweight,lowdenseandpooragainstfire.
•Examples:Pine,Fir,redwood,spruce,deodar,cedaretc.

6. DECIDUOUS
•Deciduous trees are hard wood producing trees. The leaves of this
type of trees are generally broad in size and they fall in autumn and
grow in spring. Deciduous trees are most suitable for constructional
purposes. Timber of deciduous trees is dark colored, dense, heaviest
and good against fire.
•Examples: Maple, Mahogany, Oak, teak, walnut, babul etc.

7. ENDOGENOUS
2. Endogenous trees are inward growing trees which contains fibrous
mass in their longitudinal section. The timber from these trees is useful
in some limited engineering purposes.
•Examples: bamboo, palm, cane etc.

8. STRUCTURE OF A TREE
•1. Macrostructure
The structure of a tree which is visible to the naked eye is called macro
structure of tree. Macrostructure of tree contains following components.
•Pith
•Heart wood
•Sap wood
•Cambium Layer
•Inner bark
•Outer bark
•Medullary rays

9. PITH
•The core part or innermost part of the tree is called as pith. It contains
cellulose tissues which are helpful for the growth of plant during its
young age.

10. HEART WOOD
•Heartwoodistheportionaroundthepithwhichisdarkincolorand
containsomeannualringsinit.Itisveryhardandprovidesrigidityto
thetree.Heartwoodisusedforseveralengineeringpurposesbecause
ofitsstrengthanddurability.

11. SAP WOOD
•Sapwoodcontainouterannualrings.Thisindicatestherecentgrowth
oftreeandislightincolor.Itcontainssapwhichhelpsinthegrowth
oftress.

12. CAMBIUM LAYER
•Cambiumlayercontainssapwhichwillturnintosapwoodaftersome
time.Itshouldnotexposedtoatmosphereotherwisethetreemay
dead.

13. INNER BARK
•The protecting layer of cambium layer is known as inner bark.

14. OUTER BARK
•The outermost layer of the tree section is called outer bark or cortex.
It contains cells of wood fiber.

15. MEDULLARY RAYS
•Theraysextendingfrompithtocambiumlayerareknownas
medullaryrays.Theseraysholdtheannualringsofsapwoodand
heartwoodtogether.

16. MICROSTRUCTURE
•Microstructureofatreecanonlybevisiblewithgreatmagnifications.
Itcontainscellsofdifferentshapesandsizes.Thesecellsare
responsibleformanyactionslikenutrientstransporttobranchesfrom
stem,strengthoftreeetc.

17. PROCESSING OF TIMBER
1.Felling of Trees
2.Seasoning of Timber
3.Conversion of Timber
4.Preservation of Timber

18. FELLING OF TREES
•Fellingoftreesisnothingbutcuttingoftreeswhichare
suitableforengineeringpurposes.Fellingshouldbedone
whenthetreeismatured.Thenonlyitcontainsmoreamount
ofheartwoodthansapwood.Theperfectageoftreesfor
fellingvariesfrom50to100years.Thebestseasonforfelling
oftreesisMid-winterforplainareasandmid-summerfor
hillyareas.
•Firstlyacutismadeatthelowermostpartofthetrunkona
sidewheretreeisexpectedtofell.Thecutshouldbebeyond
centerofgravityoftree.Thenprovideparallelcutwhichis
exactlyoppositetothefirstcut.Thentieupthetreetopwith4
ropeson4sides.
•Nowpulltheropeoffirstcutsideandloosentheropeonthe
oppositeside.Usingothertworopesswingthetreeslowly.
Thenthetreestartsbreakingalongthecutsandgentlyfallon
theground.Thebranchesarechoppedoff,barkisremoved
andiscutintorequiredsizes.

19. SEASONING OF TIMBER
•Seasoningoftimbermeansremovalofmoisturecontentfromtimber.
Anewlyfelltreecontainswaterupto50%ofitsdryweight.The
timbercontainsfreemoistureandboundmoisture.
•Freemoistureispresentintimberaswatervaporwhilebound
moistureispresentincellwalls.Whenitisallowedtoseasoning,free
moistureevaporatedfirstandthispointiscalledasfibersaturation
point.
•AfterFibersaturationpoint,thetimberwillshrinkondryingwhichis
nothingbutevaporationofboundmoisture.

20. THERE ARE TWO METHODS OF
SEASONING ARE THERE NAMELY
•Natural seasoning
•Artificial Seasoning

21. CONVERSION OF TIMBER
•Conversionoftimberistheprocessofcuttingoftimberintorequired
sections.Thiscanbedonebyusingpowermachines.Skilledpersons
shouldberequiredforeconomicconversionoftimber.Theconversion
canbedonebyfourtypesasfollows
•Ordinarysawing
•Tangentialsawing
•Quarterawing
•Radialsawing

22. ORDINARY SAWING
•Itisthemostusedandeasymethodofsawing.Thecuttingisdone
throughthesectionoftimberpieceatperpendiculartotheannual
rings.Wastageoftimberisminimuminthiscase.
•Theobtainedplanksarenotofequalstrength.Theouterplanks
containsapwoodandshrinksmorewhiletheinnerportionplanks
containheartwoodwhichshrinksless

23. TANGENTIAL SAWING
•Inthistypeofsawingthecutsaretangentialtoannualringsandthey
meeteachotheratrightangles.Thismethodissuitablewhenthe
annualringsareverydistinctwitheachother.

24. QUARTER SAWING
•Inquartersawing,thecutsaremaderightanglestoeachother.Thisis
suitablewhenthetimberhavenodistinctmedullaryrays.

25. RADIAL SAWING
•Inthistypeofsawing,thecutsaremadeparalleltothemedullaryrays
radially.Inthismethodwastageoftimberismaximum.

26. PRESERVATION OF TIMBER
•Thefinalstageoftimberprocessingispreservationwhichiscarried
outtoincreasethedurabilityoftimberandalsotoresisttheattacksof
fungi,insectsetc.ontimber.IngeneralASCU,Coaltar,Oilpaints,
Solignumpaintsetc.areusedaspreservatives.