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This lesson covers the stock forms, types, and standard sizes in which materials are supplied, as required by AQA GCSE D&T (8552), Section 3.2.6. Understanding stock forms is essential for practical work (knowing what to order) and for the exam (specifying appropriate starting materials for a given manufacturing process).
Stock forms are the standard shapes and sizes in which raw materials are supplied by manufacturers and suppliers. Using standard stock forms is more economical than having custom sizes produced, and they are readily available from suppliers.
| Stock Form | Description | Common Sizes |
|---|---|---|
| Rough sawn | Timber sawn from the log but not planed; rough surfaces with visible saw marks | Various; oversized compared to PAR equivalent |
| Planed all round (PAR) | All four faces planed smooth and parallel; ready to use | 12x44, 20x44, 20x70, 20x95, 20x145, 44x44, 44x70, 44x95, 44x145 mm (common finished sizes) |
| Planed square edge (PSE) | Two faces and one or two edges planed | Similar to PAR |
| Dowel rod | Round cross-section, smooth | 3, 4, 5, 6, 8, 10, 12, 15, 20, 25 mm diameter |
| Mouldings | Shaped cross-sections | Skirting, architrave, dado rail, picture rail, scotia, quadrant — standard profiles |
| Board | Standard Sheet Size | Common Thicknesses |
|---|---|---|
| MDF | 2440 x 1220 mm (8ft x 4ft) | 3, 6, 9, 12, 15, 18, 25 mm |
| Plywood | 2440 x 1220 mm | 3, 4, 6, 9, 12, 18, 25 mm |
| Chipboard | 2440 x 1220 mm | 12, 15, 18, 22, 25 mm |
| Hardboard | 2440 x 1220 mm | 3, 6 mm |
AQA Exam Tip: The standard sheet size for manufactured boards (2440 x 1220 mm — equivalent to 8 feet x 4 feet) is worth knowing. If an exam question asks about material requirements for a project, you can reference this standard size to calculate how many sheets you need and estimate waste.
| Stock Form | Cross-Section | Common Materials | Common Use |
|---|---|---|---|
| Sheet | Flat, thin (0.5-3 mm) | Mild steel, aluminium, copper, brass | Enclosures, brackets, panels, decorative work |
| Plate | Flat, thick (3 mm+) | Mild steel, aluminium | Structural steelwork, base plates, heavy fabrication |
| Flat bar | Rectangular solid cross-section | Mild steel, aluminium, brass | Brackets, frames, structural components |
| Round bar | Circular solid cross-section | Mild steel, aluminium, brass, stainless steel | Shafts, pins, turned components (lathe work) |
| Square bar | Square solid cross-section | Mild steel, aluminium | Structural frames, handles |
| Hexagonal bar | Hexagonal solid cross-section | Mild steel, brass, stainless steel | Bolts, nuts, fittings (the hex shape allows spanners to grip) |
| Round tube | Circular hollow cross-section | Mild steel, aluminium, copper, stainless steel | Bicycle frames, furniture, plumbing, handrails |
| Square tube | Square hollow cross-section | Mild steel, aluminium | Furniture frames, structural framing, go-kart chassis |
| Rectangular tube | Rectangular hollow cross-section | Mild steel, aluminium | Structural members, frames |
| Angle | L-shaped cross-section | Mild steel, aluminium | Shelf brackets, frame construction, edging |
| Wire | Very thin, round, flexible | Mild steel, copper, brass, stainless steel, aluminium | Electrical wiring, fencing, springs, sculpture |
| Extrusion | Custom complex cross-section | Aluminium (most common) | Window frames, heat sinks, curtain tracks, structural profiles |
| Stock Form | Description | Common Materials | Common Use |
|---|---|---|---|
| Sheet | Flat sheets, various thicknesses | Acrylic, HIPS, HDPE, PP, PVC, ABS, polycarbonate | Vacuum forming, laser cutting, fabrication |
| Rod | Solid round or square bar | Nylon, acetal, PTFE, acrylic | Lathe turning, machining |
| Tube | Hollow round section | Acrylic, PVC, PP, ABS | Display, plumbing, electrical conduit |
| Pellets / granules | Small pellets (~3-5 mm) | Most thermoplastics | Feed stock for injection moulding and extrusion machines |
| Film | Very thin, flexible sheet (<0.5 mm) | LDPE, PP, PET | Packaging wrap, bags, labels |
| Filament | Thin wire, typically on a spool | PLA, ABS, PETG, nylon, TPU | 3D printing (FDM/FFF) |
| Foam (block or sheet) | Expanded cellular structure | EPS (polystyrene), PU (polyurethane), EVA | Packaging, insulation, cushioning, model making |
| Liquid resin | Liquid in containers | Polyester resin, epoxy resin | Casting, laminating (GRP, CFRP), 3D printing (SLA) |
| Stock Form | Description | Common Use |
|---|---|---|
| Fabric roll (bolt) | Continuous roll, typically 1-1.5 m wide | Clothing manufacture, upholstery, curtains |
| Yarn / thread | Continuous filament on spool or cone | Sewing, knitting, embroidery |
| Non-woven sheet (felt) | Fibres bonded without weaving | Craft, insulation, filtration |
| Wadding / batting | Thick, soft sheet of loose fibres | Quilting, padding, insulation |
| Interfacing | Stiff fabric applied to the back of fabric to add structure | Collars, cuffs, waistbands |
| Question to Ask | Why It Matters |
|---|---|
| What manufacturing process will be used? | The process determines the required stock form (e.g. injection moulding needs pellets; vacuum forming needs sheet) |
| What is the final shape of the product? | Starting with a stock form close to the final shape minimises waste and processing |
| How much material is needed? | Buying standard sizes and planning cuts minimises waste and cost |
| What is the production volume? | One-off may use sheet/bar cut to size; mass production may use pellets or coil |
| Manufacturing Process | Required Stock Form |
|---|---|
| Injection moulding | Polymer pellets/granules |
| Vacuum forming | Thermoplastic sheet |
| 3D printing (FDM) | Polymer filament |
| Turning (lathe) | Metal or polymer round bar |
| Laser cutting | Sheet (timber, metal, or polymer) |
| Sand casting | Metal ingots or scrap (melted) |
| Extrusion | Metal billets or polymer pellets |
AQA Exam Tip: An exam question may describe a manufacturing process and ask you to specify the appropriate stock form. Think about what the machine needs as input: a lathe needs bar or rod; a vacuum former needs sheet; an injection moulder needs pellets. This is a straightforward way to score marks.
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