DEFECTS IN TIMBER

DEFINE DEFECTS IN TIMBER

A DEFECT IS AN IRREGULARITY OR ABNORMALITY OCCURING IN OR ON WOOD WHICH IS RESPONSIBLE FOR ITS

STRENGTH REDUCTION LOWERING OF DURABILITY LOWERING OF UTILITY POOR APPEARANCE DECAY

CLASSFICATION OF DEFECTS

CAUSED DUE TO:

NATURAL FORCES INSECTS CONVERSION SEASONING FUNGI

DEFECTS DUE TO NATURAL FORCES

CHEMICAL STAIN RIND GALLS SHAKES UPSETS TWISTED FIBRES KNOTS BURLS

CHEMICAL STAIN:- THE WOOD IS SOMETIMES DISCOLOURED BY THE CHEMICAL ACTION CAUSED WITH IT BY SOME EXTERNAL AGENCY. THIS IS KNOW AS CHEMICAL STAIN.

RIND GALLS:- THE RIND MEANS BARK AND GALLS MEANS ABNORMAL GROWTH. HENCE PECULIAR CURVED SWELLING FOUND ON THE BODYOF THE TREE ARE KNOW AS RIND GALLS.THEY DEVELOP ATPOINTS FROM WHERE BRANCHES ARE IMPROPERLY CUTOFF OR REMOVED.SO THE TIMBER IN THIS PART IS VERYWEAK AND NOT DURABLE.

SHAKES:- THEY ARE THE LONGITUDINAL SEPARATIONS IN WOOD BETWEEN THE ANNUAL RINGS. THESE ARE THE CRACKS WHICH PARTLY OR COMPLETELY SEPARATE FIBRES OF WOOD. THE SEPARATIOON MAKE THE WOODUNDESIRABLE WHEN APPERANCE IS IMPORTANT.

TYPES OF SHAKES STAR SHAKES CUP SHAKES HEART SHAKES RING SHAKES

STAR SHAKES - THESE ARE THE CRACKS WHICH EXTENDED FROM BARK TOWARDS THE SAP WOOD. THESE ARE WIDER AT OUTSIDE ENDS AND NARROWER AT INSIDE ENDS. THEY ARE USUALLY FORMED DUE TO EXTREME HEAT OR SEVERE FROST DURING THE GROWTH OF THE TREE.

CUP SHAKE - IT APPERS AS CURVED SPLIT WHICH PARTLY OR WHOLLY SEPERATES ANNUAL RINGS FROM ONE ANOTHER. IT IS CAUSED DUE TO EXCESSIVE FROST ACTION ON SAP PRESENT IN THE TREE ESPECIALLY WHEN THE TREE IS YOUNG.

HEART SHAKES - THESE CRACKS OCCUR IN CENTRE OF CROSS SECTION OF TREE.THESE CRACKS APPEAR DUE TO SHRINKAGE OF INTERIOR PART OF TREE WHICH IS APPROACHING MATURITY. THE HEART SHAKE DIVIDE THE TREE CROSS SECTION INTO TWO OR FOUR PARTS.

RING SHAKE- WHEN CUP SHAKES COVER THE ENTIRE, THEY ARE KNOWN AS RING SHAKE.

UPSETS:-THESE INDICATE WOOD FIBRES WHICH ARE INJURED BY CRUSHING OR COMPRESSION. THE UPSETS ARE MAINLY DUE TO IMPROPER FEELING OF TREE AND EXPOSURE OF TREE IN ITS YOUNG AGE TO FAST BLOWINGWIND.

TWISTED FIBRE:-THESE ARE KNOWN AS WANDERINGHEARTS AND CAUSED BY TWISTING OF YOUNG TRESS BY FAST BLOWING WIND. THE TIMBER WITH TWISTED FIBRES ARE UNSUITABLE FOR SAWING.

KNOTS:- THESE ARE THE BASES OF BRANCHES OR LIMBS WHICH ARE BROKEN OR CUT OFF FROM TREES. THE PORTION FROM WHICH THE BRANCH IS REMOVED RECEIVES NOURISHMENT FROM THE STEM FOR A PRETTY LONG TIME AND IT ULTIMATELY RESULTS IN FORMATION OF DARK HARD RINGS WHICH ARE KNOWN AS KNOTS. AS CONTINUITY OF WOOD FIBRES ARE BROKEN BYKNOTS, THEY FORM A SOURCE OF WEAKNESS.

CLASSIFICATION ON SIZE BASIS PIN KNOT – DIAMETER UPTO 6.50MM SMALL KNOT – DIAMETER UPTO 6.5 AND 20MM MEDIUM KNOT – DIAMETER BETWEEN 20 AND 40MM LARGE KNOT – DIAMETER GREATER THAN 40MM

CLASSIFICATION ON FORM AND QUALITY B BASIS

DEAD KNOT- KNOT WHICH IS SEPERATED FROM THE BODY OF WOOD. IT IS NOT SAFE TO USE WOOD WITH SUCH A KNOT FOR ENGINEERING PURPOSES.

DECAYED KNOT – POPULARLY KNOWN AS UNSOUND KNOT AND FORM BY ACTION ON FUNGI ON WOOD.

LIVE KNOT - IT IS THROUGHLY FIXED IN WOOD AND CANNOT SEPERATED OUT FROM BODY OF WOOD. IT IS FREE FROM CRACKS AND DECAY . WOOD CONTAINING THIS KNOT CAN BE USED FOR ENGENEERING PURPOSES.

LOOSE KNOT- IT IS PRELIMINARY STAGE OF DEAD KNOT. ROUND KNOT- THE CROSS SECTION OF THIS TYPE OF KNOT IS EITHER

ROUND OR OVAL TIGHT KNOT- IT IS PRELIMINARY STAGE OF LIVE KNOT. THE FIBRES OF

KNOT ARE FIRMLY HELD IN SURROUNDING WOOD.

BURLS:- THEY ARE PARTICULARLY FORMED WHEN A WHEN A TREE RECEIVES SHOCK OR

INJURY IN ITS YOUNG AGE. DUE TOITS INJURY, THE GROWTH OF TREE ISCOMPLETELY UPSET AND IRREGULAR

PROJECTIONS APPEAR ON THE BODY OFTIMBER.

WIND CRACKS:-THESE ARE THE CRACKS ON THE OUTSIDE OF A LOG DUE TO THE SHRINKAGE OF EXTERIOR SURFACE.

DEFECTS DUE TO CONVERSION

CHIP MARKDIAGONAL GRAINTORN GRAIN WANE

CHIP MARK:- THIS DEFECT IS INDICATED BY MARK OR SIGNS PLACED ON FINISHED SURFACE OF TIMBER. THEY MAY BE FORMED BY PLANNING MACHINE.

DIAGONAL GRAIN:-THIS DEFECT IS FORMED DUE TO IMPROPER SAWING OF TIMBER. IT IS INDICATED BY DIAGONAL MARKS ON STRAIGHT GRAINED SURFACE OF TIMBER.

TORN GRAIN:- DEFECT CAUSED WHEN A SMALL DEPRESSION IS FORMED ON A FINISHED SURFACE OF TIMBER BY FALLING A TIMBER OR SO.

WANE:- THIS DEFECT IS DENOTED BY PRESENCE OF ORIGINAL ROUNDED SURFACE ON MANUFACTURED PART OF TIMBER.

DEFECTS DUE TO SEASONING

TWISTCUPBOW SPRING

TWIST:- WHEN A PIECE OF TIMBER HAS SPIRALLY DISTORTED ALONG ITS LENGTH, IS KNOWN AS TWIST.

CUP:- THIS DEFECT IS INDICATED BY CURVATURE FORMED IN TRANSVERSE DIRECTION OF TIMBER. BOW:- THIS DEFECT IS INDICATED BY CURVATURE FORMED IN DIRECTION OF LENGTH OF TIMBER. SPRING:- IS THE CURVATURE OF THE PIECE OF SAWN TIMBER IN THE PLANE OF ITS WIDE FACE: KNOWN AS CROOK OR FREE SIDE BEND.

DEFECTS DUE TO FUNGI

BLUE STAINBROWN ROTDRY ROTHEART ROTWET ROTWHITE ROT

BLUE STAIN:- THE SAP OF WOOD IS STAINED TO BLUISH COLOR BY THE ACTION OF CERTAIN TYPE OF FUNGI.

BROWN ROT:- THE TERM ROT IS USED TO INDICATE