IGCSE Design & Technology
10 J
oining and Assembly
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10. Joining and assembly
● Temporary joining is a process that can be reversed
● Permanent joining is a process that cannot be reversed
● Brazing is melting a third metal (often brass) onto joint two pieces of metal with brazing
torch which cools and solidifies
● Soldering is type of brazing using lower melting point alloy as filler material
○ Weaker than brazing
○ Soft soldering is used to join copper brass or thin plate by flowing along cleaned
component (200°)
○ Hard soldering is used for stronger joint (625°)
● Welding is heating metal to extreme temperature causing components to melt and join
together
○ Filler material is used to keep molten metal clean and from
oxidation
■ Oxidation is when oxygen reacts with nearby metal
and corrodes producing a red brown layer called rust
○ Electric-arc use electricity to generate spark to melt
○ Oxy-acetylene use flammable gas mixed with oxygen
○ Welding helmet for eye protection
● Riveting is small piece of metal usually dome shaped inserted into a
hole of two component and deformed (by rivet gun or ball pein hammer) so
that it cannot be removed
○ Countersunk rivet allows revite to sit on a countersink hole where it is
leveled with the surface
○ Snap and set rivet is rivet trimmed by pinchers, hammered on both
deformed ends and snap & set is added to from smooth dome
1
○ Pop rivet is placed in the hole and rivet gun pushes the pin backward and deforms
the other end, great for when only one side can be reached
● Wood joints are used in wood, some require adhesive (finger joint) and some does not
(dovetail joints)
● Knock down fittings (KD) allows wood components to be joined easily at home with
minimal equipment, wooden or plastic corner block with drilled holes are screwed into
place
○ This is cheaper as it uses less different fittings and reduce inventory for
manufacture, flat packed to easy to transport, easier for user to build as less likely
to use wrong fitting
○ One piece: block is pressed into corner and screwed in to the component
○ Two piece corner block: allows components to be unscrewed supported by
steel pins
○ Scan fitting: pull pieces securely by steel barrel tightened to the screw piece
○ Leg fastening: for joints that can be taken apart, hanger bolt remains and screw
is unscrewed
● Cam lock: requires a shallow hole drilled and cam is turned to lock the piece in location
location
● Pre-manufactured components
○ Different screwdriver is used to prevent casual user from removing for security
○ Wood screw: smooth shank below the head, tapered point for wood
○ Machine screw: for metal, thread up to the head(tip)
2
○ Nuts and bolts: two piece where nut turned into bolt and excess is trimmed off,
(M5 x 45mm means diameter 5 mm and length 45 mm)
○ Nail: commonly used in timber (more in soft wood) as they can bend a distort in
dense hardwood
○ Hinges: connect to two piece of material that needs to move, screwed in wood
and mounted with nuts and bolt in metal, can be decorative
○ Butt hinge, butterfly hinge, flush hinge, barrel hinge, concealed hinge (adjuable),
continuous hinge
○ Catches: secure lid to boxes, closed doors on cabinet
○ Locks: secure lid to boxes, closed doors on cabinet
○ Latches: secure lid to boxes, closed doors on cabinet
● Adhesive join material by glueing them together, need to consider time to set, situation
(exposure to air, evaporate, force chemical reaction, set or cure), health and safety, in well
ventilated room
○ Acrylic cement: joining acrylic and other plastic, melt the surface then fuse
together
○ Contact adhesive: join polystyrene and fabric, fixing layers or coating
3
○ Epoxy resin: join metal and plastic, mixed with hardener to cure
○ PVA (polyvinyl Acetate): construction and assembly of timbre products, some are
water resistant
○ Synthetic resin: join wood when PVA is not suitable, water resistant, mixed prior
application
● Construction in wood
○ Carcase/ box construction: plant of wood joined to form box shapes eg cabinets,
drawers, tool boxes
○ Stool frame construction: supporting frame is made from legs and rails eg table,
chairs, stools
○ Flat frame: several pieces of wood joined to make flat shapes eg doors, window
frames, picture frames
○ Slab construction: sheets usually manmade board joined together with
permanent or KD joints (more modern) eg cement flooring, built in furniture, self
assembly furniture kits
