Unit 5B - Timber

2 types of timber finishes

1. Rough sawn
2. Planed all round (PAR)

Uses of rough sawn timber

1. Exterior tasks
2. Where finish doesn’t matter

Uses of PAR

1. Furniture
2. Internal features


1. Windows
2. Doors

Seasoning

Reduction of moisture content in timber

Common moisture contents

1. Green timber: >50%
2. Exterior use:

Air-drying

Timber is stacked so that air can circulate

Air-drying time

\~25mm/year (plank thickness that seasons)

Air-drying results

Moisture content reduces to 18% (in the UK)

Kiln-drying

Heat and pressure is used to reduce moisture content

Kiln-drying advantages

1. Lower moisture content
2. Less prone to faults
3. Kills bacteria/insects that might attack wood
4. Faster process - can be sold sooner
5. No land needed for storage whilst seasoning takes place

Kiln-drying disadvantages

1. More expensive
2. Bad for the environment

Manufactured board

Natural timber is combined with adhesive

Waste, low-grade and recycled timber can be used

Usually a pale brown natural finish

Methods of manufactured board production

1. Lamination
2. Compression

Lamination

Layers of wood are bonded together with adhesives

Compression

Wood is shredded/chipped/pulped → heated and compressed under high pressure

Normally adhesives bond the particles together

Laminated boards

1. Plywood
2. Blockboard

Compressed boards

1. OSB (oriented strand board)
2. MDF (medium density fibreboard)
3. Chipboard
4. Hardboard

Veneer

Thin slice of natural timber

Veneer uses

Manufactured boards are covered in them

Commonly seen on MDF and plywood

Methods of veneer production

1. Rotary
2. Knife cut

Rotary veneer production

Manufactured boards advantages

1. Available in large sheets & very stable - saves time joining narrow planks together
2. No defects/faults - less waste
3. No knots/resink pockets - avoids waste & protects tools that blunt easily
4. Smooth finish
5. Use low grade, recycled and waste wood
6. Many finishes, veneers and laminates

Manufactured boards disadvantages

1. Adhesives can contain hazardous particles or VOCs
2. Machining some (e.g. MDF) releases small particles - easily inhaled (even w/ mask)
3. Tools can blunt easily due to adhesive
4. Common wood joints are ineffective
5. Edges are hard to finish
6. Prone to absorb moisture

Wood is sustainable

We can grow new trees to replace those used for timber and fuel

Unsustainable timber supply

Often obtained illegally

Used much faster than it can be replaced

Problems of unsustainable timber supply

Desertification - land degradation where an area becomes increasingly less fertile and changes itself to a desert by losing flora/fauna - caused by deforestation

Contributes to global warming

Provenance of wood

Supplier should prove that wood is sustainably harvested

Organisations that ensure timber supply is regulated

1. FSC (Forest Stewardship Council)
2. PEFC (Programme for the Endorsement of Forest Certification)

Measurement format

*Length x width x thickness* - planks/boards

*Length x diameter* - rods/dowels

Manufactured boards sizes

Series of standard sizes

Thickness starts at 3 & 4mm, from 6mm goes up in threes - 9mm → 12mm etc.

Single veneer thicknesses

Thicknesses range from 0.4 → 4.5mm - commonly 1.5mm

Manufactured board sheets

Full sheet is *2440 x 1220 mm* - based on old imperial standard of *8 x 4 feet*

Boards are usually available in half/quarter sheets and commonly smaller

Many DIY and timber stores offer cutting services for exact sizes

Plank widths

Widths increase in 25mm stages - based on an imperial inch

Common size is *50 x 25 mm* - frame and carcass construction (rough sawn)

PAR would be \~ *45 x 20 mm* ∵ material removed on all sides for planing

PAR sizes always 2-3mm less per side in width & thickness - 5mm less width & thickness will be available

Reduction must be considered - inaccurate construction sizes

Plank lengths

Lengths vary, often bought by metre

Commonly 1.2m, 1.5m, 1.8m, 2.4m, 3m, 3.6m, increasing to max 4.8m

Moulding

Specially shaped section of wood

Architrave

Common type of moulding around door frames

Skirting board

Another form of moulding in older-style houses

Dowel rods

Circular sections of timber, can be ridged for use in wood joints

Woodscrews

Join 2 pieces of wood

Different lengths and diameters

Different driving methods - slotted/Phillips/Pozidriv most common

Allen & Torx becoming used more - more reliable connection with powered screwdrivers so fewer stripped heads

Dovetail nailing

Skewing nails or pins at an angle so that there is less chance that they come loose through force or vibrations

Round wire nail

All-purpose, wide flat head, can galvanise it for exterior use

Panel pin

Thin diameter, discrete small head, pin punch used to set below surface

Clout pin

Very wide head, often galvanised, used in roofing felt and plasterboard

Oval wire nail

Shaped nail, small head, prevents splitting, best for interior use

Tack

Sharp, short wide head, used to attach material e.g. upholstery to wood

Lost head nail

Thicker panel pin, used where head shouldn’t be visible, pin punch used

Knock-down fittings

Temporary

Join 2/sometimes 3 pieces of wood usually with screws

Easily dismantled for storage/transportation

Flat pack furniture relies on them

Connecting/block fitting

Cross dowel fitting

Cam lock fitting

Hinges

Attach door, windows etc. to frames/carcases

Usually metal, commonly polished brass or steel

Sold in pairs

Rebating

Recessing the hinge to ensure flush fit

Butt hinge

Standard for doors/windows

Needs rebating

Flush hinge

Less robust than butt hinge

No rebating

Butterfly hinge

Decorative version of butt hinge

Used in cabinets

Piano hinge

Long, butt style hinge

Cut to required length

Fine, close join possible

Concealed hinge

Flat pack furniture

Specialist jig needed

Tee hinge

Galvanised/painted/black japanned for outdoor use on sheds and gates

Factors in drilling

1. Drill bit type - correct amount of material removed
2. Speed - slower if bit is larger to avoid scorching wood
3. Depth - may not want to fully drill through
4. Feed rate - avoid excessive strain on drill bit

Pillar drill

Accurate

Can drill larger holes in thicker materials

Cordless drill

Adaptable

Variable speeds for drill

Clutch can help avoid over-tightening

Wood drill bit

Drill holes in wood

Flutes remove waste

Twist drill bit

General purpose bit - also used on plastic and metal

Countersunk bit

Bit for countersunk screw holes - allows screw to be flush

Hole saw

Drills large holes

Easily overheats ∵ high peripheral speed

Flat bit

Efficiently makes large holes

Efficiently removes waste

Long shank for greater depth

Forstner bit

Accurate hole-cutting bit

Good for flat-bottomed/partial thickness holes

Saws

Tenon, rip, cross-cut, coping and band

Cut material and joints to size

Saws for cutting straight lines

Tenon saw, rip saw, cross-cut saw

Saw for cutting joints

Tenon saw

Saw for cutting large panels

Rip and cross-cut saw

Saw for curved lines

Coping saw

Band saw

Powered saw

Straight cuts/gentle curves in thick/thin material

Scroll saw

Powered saw

Curves in thin material

Smoothing plane

Removes very thing layers

Smooths/flattens along grain

Chisel

Different versions

Used with mallets to form rebates/recesses

Rasp

Like a file

Very rough teeth - fast material removal

Different profiles

Surform

Fast material removal

Sharp but brittle grater-like blade

Different profiles

Disc/Belt Sander

Sand easy to reach sections

Material safely held

Bobbin sanders

Cylindrical - sand internal curves

Glasspaper

Best for hard-to-reach areas

Apply different amount of force

Different grades measured in grit density

Lower grits are coarse and scratch, higher grits are smooth and polish

Wood lathes

Turn bowls/spindles

Slower speed for larger diameter

Special chisels - scraper, gouge, parting tool

Former/Jig

Used in laminating

Object held against them, pressure applied with clamps/vacuum

Curves can be quite complex

Bending wood

Can make ornate shapes and curves

Soaking in water - increases moisture content and makes wood more flexible

Steaming

1hr/25mm of thickness - steamer box is faster

Thinner wood = tighter radius

Wood bent around former, clamped (same as laminating), dry for 1 hour

Few days to dry

Best/Worst woods for bending

Best - oak, hickory, elm, walnut and ash

Softwoods/tropical hardwoods generally don’t bend as well

Butt join

Weak - little surface area for adhesive

Pins/nails common

Dowelled joint

Wooden dowels add strength and rigidity

Dowels glued for strength

Mitre joint

Ends cut to 45°

More attractive than butt joint - used in picture frames/surrounds

Weak - little surface area

Metal splines can strengthen

Housing joint

Stronger joint - larger surface are for adhesives

Physical advantage - wood supported on 3 sides

Mortise and tenon joint

Used in tables/chairs

Strong - very large surface area for glue

Physical advantage - tenon

Advantages of flat-pack furniture

1. Compact - easy to transport
2. Low cost
3. Many styles & finishes
4. Easy to assemble
5. Can disassemble for storage/moving

Disadvantages of flat-pack furniture

1. Needs to be constructed - additional cost?
2. Less robust than traditional furniture
3. Can be complex to build
4. Weak to moisture
5. Chips/breaks more easily

CNC (Computer Numerical Control) routers (flat) & lathes (cylindrical)

Great repetitive accuracy

Very high level of detail

Available in large formats

Can make ornate shapes

Can work with large panels

Work quickly - screw holes/slots/patterns cut in 1 process

Can save/reuse templates - save minimise waste

Can produce large quantities of identical items

QC (Quality Control)

Checking product is made correctly - ensure dimensionally accurate, safe

Tolerance

Allowed range/variation of measurements in a product

Go/no go gauge

Set to min/max tolerance - allowed variation in measurement of a product

Place gauge onto product part - easily rejected if size is wrong

Reasons for finishes

Aesthetics & Protection

Aesthetics finishes

1. Match/contrast with existing materials
2. Enhance natural grain
3. Give a shine/sheen or matt finish