Joining Techniques

Contact adhesive:

Advantages	Disadvantages
Good strength Quick dry time/instant stick Waterproof Can be used over large areas	Can be toxic No slip time to adjust work

Uses: Applying formica and veneers

Tensol cement:

Advantages	Disadvantages
Joins thermoplastics Chemical weld (melts plastics together) Strong bond Quick drying	Lots of fumes Toxic to skin Must wear PPE (e.g. gloves) as it is harmful

Uses: Applying formica, veneers

Epoxy resin:

Advantages	Disadvantages
Very strong Waterproof Heat and chemical resistant	Takes time to cure/harden Requires two elements (resin and catalyst)

Uses: Aircraft, boats, golf clubs, skis

Polyvinyl acetate (PVA):

Advantages	Disadvantages
Produces strong bond when joining wood Can be used on cards/papers	Takes 24 hours to bond wood Requires clamps to hold work whilst hardening

Uses: Wood joints, card making, fabrics joining

Hot melt glue (glue gun):

Advantages	Disadvantages
Good bond when used in model making Relatively quick dry time	Safety issues (hot glue can burn skin) When using thin plastic glue can melt through creating gaps

Uses: Model making, model designs

Cyanoacrylate (superglue):

Advantages	Disadvantages
Very strong bond Dries instantly Can glue dissimilar materials together	Can dry too quickly Expensive Irritant to skin

Uses: Seal cuts, temporary fixes to damages, stopping runs in nylon

Polystyrene cement:

Advantages	Disadvantages
Excellent bond for joining polystyrene Chemical weld Long slip time	24 hours to harden Must be used carefully (can melt polystyrene)

Uses: Airfix models, joining polystyrene

Screws:

Used to join materials together

Advantages	Disadvantages
Holds in place well Can be removed easily	Prone to corrosion if exposed

Uses: Bedroom furniture

Nuts:

Used to lock the joint

Advantages	Disadvantages
Can be applied and removed an infinite number of times	Prone to vibration

Uses: Engineering situations where joints need to be undone

Bolts:

Passes through workpiece (Hex head bolt, coach bolt, stud)

Advantages	Disadvantages
Can be applied and removed an infinite number of times	Prone to vibration

Uses: Engineering situations where joints need to be undone

Washers:

Used to reduce friction and spread pressure (plain washer, spring washer)

Advantages	Disadvantages
Stops vibration Reduces stress on joints	Prone to vibration

Rivets:

Pop rivets use a rivet gun to join sheet metal together

Snap rivet uses snap and hammer to join sheet metal together

Advantages	Disadvantages
Quick process Only need access to one side (pop rivets) Can be used to tack work together	Not the strongest method of joining Need access to both sides (snap rivets) Hard to undo the joint

Uses: Sheet metal joining, boat hulls

Press:

Presses patterns into sheet metal

Advantages	Disadvantages
High strength in pressed parts Can be mass produced	Expensive set up cost Large runs needed to be economical Can make product heavy

Uses: Pattern making on metals

Oxy acetylene welding:

How it works:

1. Used to weld low carbon steel
2. The metal is prepared by creating a v shaped joint between to two metals
3. An oxygen and acetylene blow torch then heats the area
4. This creates a melt pool, this melt pool mixed with a steel filler rod creates the welded joint

Advantages	Disadvantages
Weld is as strong as parent metal Clean joint - no flux needed Portable equipment No electricity needed	Safety issues (gas equipment etc) Poor aesthetic joint Large heat effected zone

Uses: General engineering

MIG welding:

How it works:

1. Used to weld thin metals
2. MIG welding uses an electric arc to create heat
3. Carbon dioxide/argon is used to form a flux shield to protect the weld area from oxidation
4. Then an electrode wire (of the same material) is melted to fill the gap for the weld

Advantages	Disadvantages
Easier than oxy-acetylene welding Quicker than most welds Very strong joint	Poor aesthetics Can accidently melt through the metal if not careful

Uses: Cars, bike frames, metal barriers

Brazing:

How it works:

1. The two materials being joined are cleaned before welding
2. Then the two materials are held together using a former
3. Flux is applied to prevent the join area from oxidation
4. A welding torch then heat the join area and a brazing rod is used to fill the joint area

Advantages	Disadvantages
A good general purpose joint Cab be undertaken with little training Low bond temperature needed Can join dissimilar materials	Needs flux (if not weak joint) Metal must be cleaned before hand (time consuming) Not as strong as other welding techniques

Uses: General engineering, bicycle frame

Hard soldering:

How it works:

1. The two metals being joined is cleaned
2. Then the two materials are held together using a former
3. The metal is then heated up to the same temperature as the melting point of the solder
4. The solder is then applied to the joint area

Advantages	Disadvantages
Stronger than soft soldering Better aesthetics Can solder larger objects	More skill Higher melting point

Uses: Jewellery, ornaments, silverware, model engines

Soft soldering:

How it works:

1. The two metals being joined is cleaned
2. Then the two materials are held together using a former
3. The metal is then heated up to the same temperature as the melting point of the solder
4. The solder is then applied to the joint area

Advantages	Disadvantages
Low melting point Quick process Little skill	Weak joint Only suitable for small objects

Uses: Electronics

Traditional wood joints:

Large contact area required for all wood joints (dovetail, comb, housing, half lap, dowel, mortise and tenon)

Dovetail joint:

Advantages	Disadvantages
Multi-directional strength Large glue area Can't be pulled apart Aesthetically pleasing	Difficult to make Need accuracy so time/labour intensive

Uses: Drawers, office tables

Comb joint:

Advantages	Disadvantages
Makes straighter joint Less wood gets wasted during manufacture Cost effective Durable for verticle load	Can come out crooked Harder to achieve a smooth wall

Uses: Box construction, small scale projects

Housing joint:

Advantages	Disadvantages
Joint can't be seen	Not very strong

Uses: Framework construction, cabinets, shelving

Half lap joint:

Advantages	Disadvantages
Quick to make Large contact area Easy/low skilled	Quite a weak joint/needs renforcing

Uses: Simple frames or boxes

Dowel joint:

Advantages	Disadvantages
Dowling is a quick process It helps to ensure a neat finish There is no need for screws, nails or other equipment Dowel joints are the strongest type of joints when it comes to woodworking, especially when using multiple rows of dowels Dowels help to create strong joints that are easy to make at home	Misalignment of joints can lead to more waste Dowel shearing can occur if load exceeds strength No face to face grain contact

Uses: Flat pack furniture, bookcases, wardrobes, Ikea furniture

Mortise and Tenon joint:

Advantages	Disadvantages
Strong joint Clean/aesthetically pleasing joint	High accuracy needed to be made correctly Slow/labour intensive

Uses: Frame constructions, tables, chairs

Knock-down fittings:

Knock-down (KD) fittings are used to manufacture flat-pack furniture

They are easy to use and are built by the user with simple tools that are supplied with the product

Modesty block:

Moulded holes that take screws that are used to join the block to the panel (cupboards and storage units)

Barrel nuts and bolts:

Cross-dowel that is fitted into one of the pieces being joined

The bolt is then inserted through the other piece of timber and tightened

Cam-lock connectors:

Metal dowel that is screwed into one of the pieces

The cam disk is a disk that fits into a pre-drilled hole

The cam is then tightened locking the two pieces together

Wood screws:

Used to join two pieces of wood together

A pilot hole is drilled before and then the screw is screwed in using a screwdriver

Coach bolt:

Used to temporarily join wood pieced togther

Cannot rotate once it has been bolted in

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