WORKSHOP SKILLS
Kiran Prasanth R. 4th Semester Furniture & Interior Design Graduate Diploma Program in Design National Institute of Design Faculty : L .C .Ujawane
WORKSHOP SKILLS
WHAT IS WOOD ?
WHAT IS WOOD ?
W
ood is the oldest building material known to man. It is organic to nature. It is derived from the tree trunk. Wood is produced by the thin zone of cells near the outside of the trunk or branch ,just beneath the outer layer called BARK. These cells constitute the Vascular Cambium and are thin walled and delicate. It is also called MERISTEMATIC TISSUE and divides throughout the year increasing girth of the stem or trunk. More wood is added to the trunk as the crown of the tree gets longer. The cyclic production of new wood cells each spring and summer and subsequent cessation of cambial divisions each autumn and winter leaves familiar patterns in the wood, called GROWTH RINGS or ANNUAL RINGS. The prominence of these rings varies in different wood types, due to difference in cell structure and climatic conditions. Trees growing in regions were winters are harsh, have sharper and defined rings. During the beginning stages of the growing season, the tracheal have large lumen or cavity and are thin walled, helping in condition of water. The wood is called as EARLY WOOD or SPRING WOOD.
Later, the lumens become smaller and the cells help in supporting the tree and the wood is called LATE WOOD or SUMMER WOOD. The wood at the core of the trunk is harder, darker and called HEART WOOD. It consist of cells which are dead and physiologically inactive. The outer portion of wood , beneath the bark is paler in colour and is called SAPWOOD In a sapling all the wood carries the food and water necessary for the growth of this wood .This portion is responsible for active transport and physiological activities. The hardwood is darker due to enrichment of cells by extraneous chemicals called EXTRACTIVES, which slow down the natural decay of wood by fungi and also provide protection against larvae of boring insects. Thus heartwood which is produced by reduction in moisture content is used for furniture , paneling , craft ware etc. because of its appealing grain pattern and automatic property. THE TYPES OF WOOD There are two basic categories of wood: Hardwood and Softwood. Through it is usually assumed that these terms denote the
strength of wood, the difference between them is purely botanical. Softwoods are timbers of needle leaved trees. Such as pines , spruces, firs etc. They are called CONFERS. These trees are usually tall evergreen trees which retains foliage throughout the year. Hardwoods are timbers of broad leaved trees such as Oak, Ash, Elm, etc. They are usually deciduous but tropical hardwood trees retain foliage year long. Mostly softwoods are Gymnosperms and hardwoods are Angiosperms. Usually hardwoods have strong wood than softwood. But it is not applicable in all cases. Softwood have simpler, uniform cell structure. The technical serve structural and conducting purposes. Hardwoods have specialized vessels and fibers providing structural support. The range of cell types and diversity of pattern gives pleasing appearance and grain pattern and so hardwoods and used in verity of products. STRUCTURE OF WOOD Wood is composed of elongated cells whose frame work is cellulose. The cells are cemented together by lignin, and their arrangement in the tree greatly affects the appearance and properties of different species .The
45 degree or more with the surface of the piece is called Edge Grain, or Rift Sawn in softwoods and quarter sawn in hardwoods. Flat grains or plain sawn refers to lumber that has been sawed approximately tangential to growth rings. KNOTS cross-section of most trees will show certain features which are common to all trees .The important parts which make up the structure of any tree are. A.Dry, dead tissue called Outer bark which serves as a protective coating. B.Moist soft Inner bark carrying food from the leaves to the other parts of the tree. C.Microscopic layer inside inner bark – Cambium where new wood and bark cells are formed. D.Lighter Sapwood which carries sap from roots of the tree to the leaves. E.Darker, harder, inactive heartwood. F.Pith, where new growth for twigs takes place G.Wood Rays which connects various parts of a tree for the storage and movement of food. There are some more properties, exhibited by all wood types.
GRAIN The wood from rapid growing trees will have wide annual growth rings and is called coarse grained. Slow growing trees have narrow growth rings and called Close grained. Grains usually refers to the appearance of the piece. Lumber is sawed in such a manner that annual rings form an angle of
Classification of knots depends upon appearance of the knot on a sawed surface and on whether the knot is the result of a limb that was alive or dead when the tree was cut. Knots affect the strength of wood piece as the grain has to deviate from its regular direction to pass around it. CHECKS & SHAKES A CHECK is the lengthwise separation of wood across the annual growth ring and a SHAKE is a separation along the grain between the annual growth rings. A number of checks and shakes will reduce working value of the piece. MOISTURE CONTENT Wood has considerable amount of water within its free cells. After a tree is cut, the
moisture content keeps dropping. Moisture content is defined as the weight of water contained in wood, expressed as a percentage of the weight of the oven dry wood. Wood will continue to dry till it reaches ‘equilibrium’. Moisture content which depends up on atmosphere and relative humidity. SHRINKAGE After fiber saturation point [free water in cells is evaporated and cell walls are saturated] is reached, moisture content reduces and wood shrinks almost tangentially or in the direction of annual growth rings. TIMBER Timber is more than a single raw material. It consist of an immense verity of different woods from trees growing in all parts of the world. But most of worlds forest land is either not suitable for economic timber production or not sufficiently accessible. FROM TREE TO SAWN TIMBER The felled trunks or logs are brought from the forest to the nearest transport rout. Then they are transported to sawmills through rail, road or water. Floating protects the
logs from infection by insects and prevents the ends from splitting. A typical softwood sawmill has saws installed on the upper deck, angularly equipment at ground level. A sloping conveyor (jack ladder) brings up a continuous supply of logs from the log pond. The logs are sawn to provide a centre block and side boards. After sawing, timber is carried on by conveyor for trimming, grading and then is stored in the yard or placed in kilns for seasoning. Slobs
and off cuts are used for wood pulp, particle boards or firewood. Hardwoods are generally sawn by band saws installed in the mill at ground level so that heavy logs can be lifted or rolled on to the log carriage direct from the yard. Some smaller mills use circular saws or rotary saws. ‘Through and Through’ sawing is the most economical method, The log being sliced into boards and planks. The cut planks are arranged again in the form of a log to form a bouli. Quarter Sawing is a slow and expensive method used for exclusive verities like oak, Whose handsome pattern is derived from broad rays radiating from the centre.
An economical method of sawing hardwood to exclude heart centre is Wainscot cutting. The log is sawn through the heart in to two halves and one or two boards are taken off each side of the cut to eliminate defects, as the centre is subject to heart shakes. This leaves two complete half logs or ‘Wainscot bullets’ which are sawed again in to boards at right angles to original cuts. Conversion of logs in to sawn timber is not the final stage. There is a large demand for planed boards, for use as floorings, Shelving and door manufacture. Planning machines have small planers provided with cutter heads which plane each face of timber separately.
of about 50 percent .Drying also prevents decay, as wood rotting fungi will not attack timber with less than 20 percent moisture. In air drying, timber is stacked with layers of pieces separated by thin sticks to allow circulation of air. The thickness of sticks and weather regulates evaporation of moisture. Storage in a well designed drying shed is the best way to ensure that the timber dries properly and remains in good condition .If timber is pulled in the open, the top of the stack should be protected from sun and rain by water proof sheets or boards. Kilns are a mechanical and scientifically controlled means of speeding up evaporation moisture in wood, but they have the advantage that the rate of drying can be reg-
ulated to suit both the species and dimensions of the timber .The humidity inside the kiln is gradually reduced and temperature is increased to a calculated rate. Kiln drying of some thick hardwoods takes a longtime and is therefore expensive. Air seasoning is used in early stages and kilning is used for a short final drying .After seasoning the timber will eventually adjust its moisture content to surrounding air. The moisture content can be checked by portable electric moisture meter providing the surface is not unduly wet . Moisture in wood causes many difficulties, hence proper attention is to be paid to it at all stages of production and utilization.
SEASONING
MANMADE WOOD -VENEER
Seasoning of timber can more accurately be described as condoning as it is simply the adjustment of moisture content of the wood to a state of equilibrium with the atmosphere. Timber shrinks when it dries and expands when it absorbs moisture. With shrinkage, wood becomes stiffer and considerably stronger, the strength in bending of most species increasing from green to dry by an average
Wood veneer is a thin sheet of wood having grain direction parallel to surface of wood. They were made by pains taking splitting thin slates of wood and then smoothing them down to desired thickness. Today most wood veneer is rotary cut and to a lesser extend sliced with knives. Veneer is bent in to shapes in commercial basket making and also used to decorate surfaces.
PLYWOOD Plywood is composed of an uneven number of thin layers of wood veneers called PLIES. The basic principle is the cross bending of sheets of veneer so that grain of each sheet is at right angles to that of its neighbors. This helps in reduction of moisture movement, distribution of strength properties and neutralization of defects. Another advantage of plywood is that face veneer can be selected for quality and appearance in any desired type of timber and inferior grades relegated to inner core. The peeled veneers are softened by steaming, cross cut to correct length and clamped to a rotating lathe against a peeling knife, producing a continues sheet of wet veneer. The wet sheets are passed through a continues wet drier. Defects and splits are repaired and patched with clear veneer. Adhesive is applied between sheets by a glue spreading machine and plies are arranged in correct
order of grain and direction .They are pressed hydraulically and then edges are trimmed .It can be 3ply, 5ply or multiply. BLOCK BOARD Block Board is similar to plywood as it has veneer on its face and back, but the core consist of thin strips of solid wood up to 1inch wide, assembled and glued side by side. In 3ply, the face and back each consist of one or two veneers with grains at right angles to care. In 5ply ,the length exceeds width, the face and back are two veneers, The inner one with grains across the width and outer one with grain parallel to the core. Other varieties of block board are Batten boards and Lamin boards. In batten boards ,the solid wooden strips are up to
three inches wide .In lamin boards the core has thin strips of wood glued together face to face. This is very stable but expensive board. All these boards make a strong, rigid material. Which can stand alone without framing . It is used for doors, tables , desktops ,counters ,ship buildings etc. There are interior and exterior plywood’s, which use different adhesives. Interior plywood uses casein glue. Exterior plywood uses synthetic resin adhesives. There are three types: 1. Moisture Resistant (MR) – uses urea- formaldehyde adhesive and is suited for normal exterior use. 2. Boil Resistant (BR)- Uses melamineformaldehyde as bonding agent. It has greater heat and boiling water resistant. 3. Weather and boil proof (WBP) uses phenol formaldehyde and resorcinol- formaldehyde. It can withstand severe conditions and prolonged boiling. FIBRE BOARD OR HARDBOARD Small pulp wood legs are ground in to wood pulp which is fed in a liquid mass of wood fiber and water on to a wire- mesh conveyer to form a mat of 2inch thickness. Resin is added to the pulp and it is carried through a series of rollers to compress it and squeeze out bulk of water. A cross cut saw cuts out
sheets of required size and the sheets are pressed then conditioned to bring them is available in Medium, Standard and out tempered version. PARTICLE BOARD It is also called CHIP BOARD and is formed by compressing and resin bonding various types of wood chips ranging from coarse saw dust to flat sharing. This forms a flat and uniform textured board usually in thickness of 9mm to 25mm and sometimes thickness. It has good wearing properties and is free from natural defects of solid wood. It can be nailed, screwed and worked with normal woodworking tools. It can be treated with preservatives, made in a range of densities. COCONUT WOOD Coconut wood is a monocotyledon which has no separate heart wood and sapwood perimeters. It has continues vascular bundles spread throughout the length of the cellulose structure. As it is non-branching, there are no knots. It has extremely high fiber content. Only non productive trees are logged as the primary. Secondary and tertiary fibers are mature at that stage and have high density. The colour the tone, higher the density .
Coconut wood is emerging as a preferred substitute of hard wood because of low price and ecological concern. It is traditionally used in roofing, village houses, cattle shed, farm house and lasts for 50 to 60 years after treatment. Other uses are for window panes, doors, panels, cottage industry, craft products and structural applications. High density wood is used in structural applications and used in posts, tissues, floors and load bearing structures. Recently paper pulp was produced from coconut but it was found to be inferior in quality and economically unavailable. WOOD SUBSTITUTES -RUBBER WOOD Rubber is classified in to light hardwood category. The wood is whitish yellow or light cream. The grain pattern is mostly straight. Growth rings are not apparent. The large vessels in the structure of cells give attractive appearance. The wood is very durable ,gives an excellent timber feel has very little tendency to warp or crack. Rubber, when used for latex production has an economic lifespan of 25 to 30 years, after which it was used as firewood. Now due to increasing concern for preservation of tropical forest and their hardwood trees, rubber wood is being used to make building com-
ponents, furniture, household wooden ware, parquet flooring, plywood etc. BAMBOO Bamboo is a giant woody grass which puts out several, full length, ready to use culms (stems) every year .It is found in tropical and sub tropical areas. It is very adaptable and may be deciduous or evergreen called Wood of the Poor, it is used in food, cooking, and in building houses. Bamboo is the real symbol of flexibility. It is strong as steel, nuclear tough and has striking beauty. Now it is used as a sustainable for fast depending wood and is an economic alternative to material used for construction of pillars, walls, frames, rafters, room separators, railing and roofs. The most common usage now a days is for furniture, were bamboo has proved itself to be extremely efficient. Some interesting facts about bamboo : A) The needle in Alexander Graham Bells first phonograph was made of bamboo. B) Edison used bamboo filaments in light bulb manufacture. C) The suspension bridge in china is 250 yards long, 9feet wide and rests on bamboo cables, fastened over water. There is not a single piece if nail or iron in it.
RATTAN Rattans are spiny climbing palms in tropics. The strips of stem are used in furniture, cordage, construction, basketry, matting etc. and it is called ‘Cane’.
WOODWORKING JOINTS
WOODWORKING JOINTS
TENON & MORTISE
WEDGE JOINT
DOVE TAIL JOINT
BOX / FINGER / COMB JOINT
MITRE JOINT
DOWEL JOINT
PERFECT DOWEL Perfect Dowel • • • • • • •
Should not be too smooth Should be slightly rough Should be of hard wood Round shape Ends be chamfered Slight channel or groove to allow the air Should penetrate
Dowel put inside along the grain is weaker joint than across the grain. Dowel should penetrate first in smaller depth (across the grain) and remaining in the longer (along the grain) Length of the dowel should be not more than half of the length and also not more than half of the width of smaller wood. Its stronger than the Tenon & Mortise joints
HALF LAP JOINT
THREE - AXIS JOINT
TENON & MORTISE
BEAM JOINT
EDGE TO EDGE JOINERY
METAL JOINERY
UPHOLSTERY Upholstery Includes components like : 1) Structural Components 2) Cushioning Components 3) Protective Components 4) Decorative Components Basically in upholstery materials like • Plywood • Wood • Nylon thread • Metal sheet • Metal rod • Canvas • Foam • Cotton etc. are used. Then whole of it is covered with grey cloth or maybe with rexin, cotton etc.
WOOD FINISHING
WOOD FINISHING Why wood finishing ? • • • •
Longer Life Good Looks Hide Faults Unrich Materials
Abrasive paper / sand paper • [80 – 120] rough • [180 – 220 ] fine • After 320 – super fine Finishing Processes • • • • •
Surface Preparation Wood Filling Staining Scaler Finishing
Low cost Finishing materials • • • • •
Linseed Oil Wax Polish French Polish Varnish Water Base Aque
Surface preparation • Sanding is always done along the grains. • Second sanding isin circular motion. • Third again along the grain. Working radius • Edges slightly smooth not sharp. Wood Filling • Clay ( red, yellow, black, white) • For wood, take rosewood sawdust + araldite, teakwood sawdust + fevicol, Chalk Powder, Whiting Powder, White paint, Seeras (made from leather used as stiching materials) • Wooden filler like putty/ lapi, slightly grey • After filling again its sanded. Take 12 hours to 6 hours to dry (natural grain shouldn’t be hide) Staining • To give colour , clay act as both filler and stain • Sealer • Hold the material with wood Terminator • by pidilite, used to keep wood safe from termites before fixing furniture to wall.
• • • •
Wood preservative Eco friendly No harmful chemical Effective against termites
More Finishing Materials • • • • •
Linseed oil Oil made of flax seed Turpentine oil is mixed in 1:1 proportion Its very thick If drying process is to be speeded up, mix 1:2 turpentine. • No filler required, no sealer • Sand with 240 after applying oil in circular motion then along the grain • 7Rs/sq ft Advantages • • • •
Very cheap No skill required Wood Gets Darker Looks good in dark wood. In light wood like chill, pine etc it is not preferred • Matt finish Disadvantages • • • • •
Surface looks sticky Collects dust Stains fast Repeatedly polished after 6-8 months 4-8 days taken for drying.
Wax polish • 8Rs/sq ft
• Any polish can be put after this shellac coat
• Dries fast ,so chances of paches • Duration 1 – 1.5 years • Produces stain of tea / coffee
- Environment friendly, water base not suitable for Indian climate [research on] • Available in single component • Spray or brush used • Glossy and matt effect possible • Good for children furniture • 45Rs/sq ft
Varnish
Polyurethane (PU)
• Comes from wood • Copal gum : obtained from pine tree trunks after 2-3 years of cutting ( remains blow ground ) • Varnish :- Copal Varnish • :- Synthetic Varnish • Transparent slightly yellowish • Ready minimum available • Lapi or putty used as filler in this case • No need of sealer, varnish acts as sealer • Varnish is better if sprayed • Harder than others • Drying time 8 – 10 hours
• • • • • • • • • • • •
Disadvantages French Polish / Shellac coat • Shellac + methylated spirit /alcohol / thinner • Shellac mostly available in south India ,inferior quality of lac • Shellac obtained from the bark of the tree, insects suck the sapwood juice and deposit it on the bark. • Available in different colours like yellow ,reddish ,brownish • Best result when mixed with methylated spirit • Proportion 1:6, Shellac : thinner • 12Rs/sq ft Properties • Very good scaler material • Obtained from wood • Dries very fast because of thinner / alcohol • Good shining effect (glossy) • 3 coats including the filler coat 20 – 30 minutes time for drying, better 2 coats, 1st coat- 1.7 (thinner) and remaining thick. • Repolishing is easy • Suitable for light or dark wood • Excellent scaler
Touch wood – asian paint Wander wood – nerolac Wudfin – pidlite One component sometimes thinner used Synthetic material so tough finishing Heat resistant Highly durable Scratch resistant High glossy / matt Used in both hard / soft 170Rs /sq ft 20Rs /sqft
Lacquer Disadvantages • Not weather resistance • Peels or washed off • Poisonous not used in children’s furniture • 18Rs/sq ft Water base aque
• • • •
Charm Wood – Vam. Org 35Rs /sq ft Synthetic lacquer – NC(Nitro Cellulose ) Lacquer forms shining film but slightly flexible can take climatic changes • Best for Indian conditions
Melamine • two compounds pack • Apcolite natural Wood Finish- Asian paints • Wudfin – pidilite • Charm wood – VAM org. Acrylic • ( TC pack ) showcase acrylic – pidilite • 55Rs /sq ft Polyster • • • • • • • • •
Three component packs Showcase polyster – pidilite 3-4mm thick layer like glass Very hard solid Excellent glossy Very tough like mirror finish Base : accelerator : catylst (harder) 100 : 2.5 : 2.5 Polyster base and accelerator should be mixed and just prior to application mix the catylst • Like glass , can develop cracks under pressure • 300 – 350Rs /sq ft Tung Oil • another linseed oil • Sometimes they add varnish to it
• • • • •
China oil, Denish oil Warm oil absorbs faster Requires 3 coats Oil is agood Preservative, water resistant Most suitable for rosewood, teak, badam etc.
ADHESIVE
ADHESIVE
flooring) - SR x PRES Cement No 798
Animal Glue Super Glue
•
From boiling animal skin(used in England till 1930) • Casein Glue(cold water glue)- made from flour.
• • • •
FeviQuick Super Wix Elfy Fevicol FX
Thermosetting glue / Synthetic resin glue • Fevicol SH • Fevicol P (prolong) • Movicol CSA ( carpenter slone adhesive) • Fevicol REPID (fast)- not advised for big areas • Fevicol SPEEDX (for fast setting and forming) • Fevicol BWS (adhesive (resin) + Harder 4:1 ,used in moist condition , excellent water resistant) EPROXY resin adhesive • • • •
Araldite Fevitite Fevitite – rapid/super fast M Seal
Impact Adhesive • Fevibond • Fevicol SR 988/ SR 505 (for carpet
Thermoplastic Glues • Urea Formaldehyde • Phenol Formaldehyde Thermosetting • sets at the room temperature with certain chemical action
joints. • Glue has more shear strength than tension. • The principle strength of glue joint is its resistance to shear and not tension. • Joint is better in AA tension and not in BB . • The layer of the glue should be kept as thin as possible and uniformly applied. • Glue holds the material by surface contact. • Glue should be applied on both the surfaces.
Thermoplastic
Synthetic Resin Glue- Polyvinyl Acetate (PVA)
• It has to be heated and pressed • Thinner the layer of glue, the better the
•
plywood, glue is first applied on lamination . This is to make sure that the plywood doesn’t totally absorb the glue before pressing the lamination. - 2kg/sq ft weight should be given for 8 – 10 hour. - 1 kg glue for 35sqft. Increasing the glue area by 100% doesn’t lead to 100% increase in shear strength. Only 75% to 80% increase is there. As compared to butt joint, figure joint is six
times stronger. In a figure joint the proportion must be 1:6 or 1:8 to give more glue area. Eproxy Resign Adhesive
Fevitite • Setting time 5-6 hours at room temperature • 0.05mm – 0.1mm thick layer should be applied Fevitite Rapid / Superfast • Setting time 2-3 hours Impact Adhesive
• Very strong joineries • Any materials – ceramics, leather • Except – Polyurethene, Teflon, silicon, polyproplene . • Generally comes in two component pack we generally mixaraldite as 50:50. • Requires 24 hours. • Never cover with plastic while drying.
• Fevibond • Apply on both surfaces, keep for some time, stick and apply pressure. • Not suitable for layer area and doesn’t take weight • Very quick • Super Glue • Setting time 1-2seconds
ADHESIVE JOINERY
PLYWOOD JOINERY
SCREWS
NUTS
SHUTTERS
THE STOOL
THE STOOL As the part of workshop skills-1, the final assignment given in this course was to make a stool. This was the starting were a 1:1 prototype was going to be made. The condition in this assignment was to include minimum five different joineries. Teak wood, acrylic, iron rod (dowel) and some metal clamps & screws were used in the stool and wooden joineries like 1. 2. 3. 4. 5.
Half lap Box joint Dowel joint Slotted tenon & mortise Mitre joint
The stool was basically in triangular shape from top to bottom which makes it steady, stable & strong enough.
JOINERY & DIAGRAMS
ORTHOGRAPHIC DRAWING
EXPLODED VIEW
ISOMETRIC VIEW
Kiran Prasanth R. 4th Semester Furniture & Interior Design GDPD National Institute of Design Paldi, Ahmedabad Ph : 09974762449 E-mail : kiranprasanth_r@nid.edu kiranprasanthr@gmail.com