Materials & manufacture · National 5
Joining, assembly & finishing
6 cards · 5 quiz · 1 exam
Design & Manufacture · National 5 · mrkellydt.co.uk
What you're learning in this topic
Learning intention WALT
We are learning about joining, assembly & finishing, specifically to:
understand
- mortise and tenon, lap, rub, halving, dowel, rebate and housing joints and where they are used
- how to prepare and apply each surface finish: sanding, polishing, varnish, oil, stain, wax, paint, dip coating
- how to finish the edges of acrylic
be able to
- choose between PVA and epoxy resin, screws, nails, nuts and bolts, pop rivets and welding
Success criteria WILF
- I can describe mortise and tenon, lap, rub, halving, dowel, rebate and housing joints and where they are used
- I can choose between PVA and epoxy resin, screws, nails, nuts and bolts, pop rivets and welding
- I can describe how to prepare and apply each surface finish: sanding, polishing, varnish, oil, stain, wax, paint, dip coating
- I can describe how to finish the edges of acrylic
Wood joints
- Frame joints: mortise and tenon (strong; tables, chairs, frames), bridle (strong corner joint for frames), halving (simple frames), dowel (replaces traditional joints in factory furniture), lap.
- Rub joint: two planed edges glued together side by side to make a wide board (table tops, panels).
- Carcase joints: housing (bookshelves, cabinets; stopped housing looks neater), rebate (fitting back panels), butt (quick but weak), dovetail (drawers, decorative), mitre (hides end grain).
Fixings and adhesives
- Screws: countersunk (flush), round head (head can stand proud), chipboard screws. Drill a pilot hole, then a clearance hole in the top piece, then countersink.
- Nails and pins: panel pins hold glued joints while they set; oval brads less likely to split wood; punch below surface with a nail punch.
- Nuts and bolts: strong and removable.
- Pop rivets: join thin sheet from one side.
- Welding: permanent, strong joint in metal.
- PVA: general woodworking, non-toxic, about an hour to set. Epoxy resin: two parts, joins different materials (metal, plastic, wood).
- Knock-down fittings: non-permanent, for flat-pack furniture (cam locks, corner blocks, cross dowels). Allow self-assembly, easy storage and transport, avoid complex joints.
Surface finishing
- Wood: sand with the grain through finer grades, then varnish (hard, protective), oil (natural look, food safe on some), stain (changes colour), wax (sheen), paint.
- Metal: file (cross then draw filing), emery cloth, wet and dry paper, polish; then lacquer, paint or dip-coat to stop corrosion.
- Plastic (acrylic edges): file, draw file, wet and dry, then polish.
- Dip coating: heat metal in an oven, dip into fluidised plastic powder; gives a smooth, coloured, protective, comfortable finish.
- Poor finishes come from dust, runs, brush marks, skipping grades, or not removing oil and dirt.
Key terms
| Mortise and tenon | Strong frame joint for tables, chairs and doors. |
|---|---|
| Housing joint | Carcase joint for shelves in bookcases and cabinets. |
| Knock-down fitting | Non-permanent fitting for flat-pack furniture. |
| Epoxy resin | Two-part adhesive that joins different materials. |
| Pop rivet | Joins thin sheet from one side only. |
| Dip coating | Hot metal dipped in plastic powder: protective, coloured, grippy finish. |
Quick check
1. Which joint is best for fixing shelves into the sides of a bookcase?
- Housing
- Halving
- Mortise and tenon
- Lap
Show answer
A: Housing. Housings support the shelf along its width.
2. Why are knock-down fittings used in flat-pack furniture?
- They are permanent, so the product can't be taken apart
- Product can be packed flat and assembled at home
- They are stronger than any traditional wood joint
- They hide every screw, so the product looks seamless
Show answer
B: Product can be packed flat and assembled at home. Easy storage, transport and self-assembly.
3. Which adhesive would join aluminium to acrylic?
- PVA
- Wood glue
- Epoxy resin
- Glue stick
Show answer
C: Epoxy resin. Epoxy bonds dissimilar non-porous materials.
4. Before varnishing wood you should…
- Sand across the grain with a coarse paper first
- Wet the surface and varnish while it is still damp
- Apply a coat of oil to seal the grain beforehand
- Sand with the grain through finer grades and remove dust
Show answer
D: Sand with the grain through finer grades and remove dust. Preparation gives a quality finish.
5. What is the purpose of a pilot hole for a screw?
- To guide the screw and stop the wood splitting
- To let the screw head sit below the surface
- To make the screw easy to remove later
- To hold extra glue around the screw
Show answer
A: To guide the screw and stop the wood splitting. A clearance hole lets the top piece pull tight; countersinking sets the head flush.
Exam-style questions
1. Describe how a mild steel part would be prepared and finished by dip coating. (3 marks)
Show marking guidance
- Clean/degrease and remove burrs (1)
- Heat the part in the oven (1)
- Dip into the fluidiser of plastic powder, which melts onto the hot metal (1)
- Allow to cool / reheat to smooth (1)
Printable worksheet
An I do, we do, you do worksheet for this topic, with a separate answer sheet.