Timber Stockforms

WOOD - 1

Process of how timber is prepared and supplied for manufacturing, including rough-sawn and planed timber (PSE/PAR)

1. felling / debarking. the tree is cut down and branches and bark is removed. this produces the log for processing

2. conversion. logs are sawn into boards / section planks. produces usable timber sections.

3. seasoning. moisture content is reduced. improves dimensional stability.

4. grading. timber is inspected for quality / defects. ensures that the timber is suitable for intended use.

5. machining / planing. surfaces are cut or planed flat and straight. this gives accurate dimensions and smooth surfaces

6. PSE. faces and edges are square and accurately machined (3 different methods. through&through, quarter and tangential sawing. affects stability, warping and strength). this creates a consistent stock form for manufacturing.

Debarking

trees are felled

branches and bark are removed

logs are cut into manageable lengths

transported to a sawmill for further processing

Conversion

logs are cut into planks using sawmills.

What is a sawmill?

facility where logs are cut into lumber and other wood products using large saws and machinery.

transforms ray logs into usable boards / planks / beams.

feed logs through saws that slices them into desired shapes and sizes.

Seasoning

wood is seasoned before it is sold to prevent - warpage / shrinking / splitting.

wood can be air dried or kiln dried.

air dried (AD) - stored under cover and dry naturally.

kiln drying (KD) - uses steam to artificially dry timber and speed up drying process.

Why is AD timber best suited for external projects?

AD timber has a higher moisture content than KD timber, making it more suitable to use for external use where timber is exposed to changing humidity levels.

AD timber storage

traditional inexpensive method of stacking timber outdoor under a cover where stickers in between the planks to allow air to travel through and remove moisture.

Planing

seasoned plank is further processed by planing into the form of a stock form - PSE or PAR. where the rough sawn edges are removed and creates timber with dimensional accuracy.

this make the timber smaller and smoother. around 3mm is planed from each side. PSE has one square edge. PAR is square on all edges.

standard timber sizes

rough sawn - timber sold off after planing. rough and uneven surface.

planed square edge (PSE) and planed all around (PAR) timber require extra machining to make the edges square and achieve a smooth finish.

PSE - smooth / planed surfaces with square edges.

PAR - smooth and accurately sized on all four sides and ready for use.

machine to trim rough sawn timber to PSE and PAR timber

planer thicknessers

Timber categorised into -

natural timbers (hardwood / softwood) and manufactured boards.

natural timbers are available in a range of stock forms - rough sawn, PSE, PAR.

Advantages of PSE and PAR timber :

PSE - smooth and flat surfaces with square edges. makes it easier to measure / mark out / join accurately.

PAR - smooth and accurately dimensioned surface on all four sides. improved quality of the finish.

Which stock form is cheapest?

rough sawn timber - no planing or finishing. less machining and processing. both PSE AND PAR cost more due to additional machining.

Rough Sawn

characteristics
common uses
cost

characteristics - cut straight from the log. rough. splinters and uneven edges.

common uses - construction work. projects for structure rather than appearance. often used outdoors or in hidden areas.

cost - cheapest stock form. surfaces are rough from the industrial saws used in a sawmill.

Why is rough sawn timber suited for using in timber frame housing?

cost effective and hidden from view once the construction is finished.

PSE

characteristics
common uses

one edge is smooth and straight. other sides may still be rough. easier to handle and join than rough sawn.

furniture frames / shelving / DIY projects

PAR

characteristics
common uses

all sides are smooth and even. precise dimensions. ready for use.

interior furniture. cabinet making. visible woodwork. ideal for painting, staining or varnishing.

State two reasons why PAR timber costs more than rough sawn timber. [2]

(2): planing/machining takes extra time, labour and energy; material is removed so you pay for waste; smoother and more accurate finish adds value.​

Explain why MDF might be chosen instead of solid oak for a painted wardrobe door. [4]​

​

(4): MDF is smooth with no grain, so it paints well; cheaper than solid oak; stable (does not warp or split); available in large flat sheets. Award up to 2 for each developed reason.​

3. Evaluate the stock form you would choose for the visible frame of a dining chair. [6]​

(6): Level-based. Strong answers compare stock forms (rough sawn vs PSE vs PAR) against cost, appearance, accuracy of joints and finish, link to a chosen product, and reach a justified conclusion, e.g. PAR hardwood for a visible chair frame because it is smooth and accurate, although it costs more.​

Timber sizes

timber is bought and priced by its sawn (nominal) size. eg: 50×25mm

planing removes 3mm from each planed surface.

finished size is smaller than the size paid for.

use finished size in cutting lists and working out joints.

Hardwood

tree
growth
properties
examples
uses

deciduous, broad leaved tree.

slow growing (50 - 100 years) - more expensive.

dense / strong / durable with attractive grain. exception - balsa as it is very soft and light

oak. mahogany. beech. jelutong. balsa.

oak - furniture and flooring
beech - toys and handles
mahogany - quality furniture
jelutong - carving and patterns.
balsa - models and patterns

Softwood

tree
growth
properties
examples
uses

coniferous, needle leaved

fast. (20-30 years) so cheaper and sustainable.

lighter and easier to work with. more knots and resin.

pine. cedar. larch. redwood.

pine - construction and shelving
cedar - cladding and sheds
larch - fencing and boats
redwood - joinery

MDF

made from
advantages
disadvantages
uses

fine wood fibres and resin pressed

smooth. no grain. easy to machine. paints well. cheap.

swells if wet. heavy. dust is a health hazard.

flat pack furniture and painted units.

Hardboard

made from
advantages
disadvantages
uses

wood fibres compressed into a thin sheet.

cheap, smooth on one side. thin and flexible.

low strength. not water resistant.

cabinet backs and drawer bases

Chipboard

made from
advantages
disadvantages
uses

wood chips and resin pressed

cheap. stable. flat. available in large sheets.

weak edges. rough face. swells if wet.

worktop base and flat pack.

Plywood

made from
advantages
disadvantages
uses

thing veneers glued in layers. grain at 90 degrees to each other.

strong in all directions. stable. resists warping.

more expensive than MDF / chipboard. edges need finishing.

furniture and drawer bases. curved forms.