Working with Aluminium
Aluminium sections, or profiles, are designed for specific applications.
These can include:
architectural systems
The production of aluminium products relies heavily on machining as part of
the fabrication process. Machining is the mechanical operation used to
remove material from a workpiece by means of cutting tools which divide,
cut, penetrate or shape. Although the bulk of machining operations require
the use of machine power to do the work, manual operations such as sawing,
drilling and filing are regarded as machining processes. The ease or
difficulty of performing a machining operation is called machinability.
Machinability is determined by the:
Aluminium can be machined on most machines used for metal or wood. It
can also be machined using hand tools such as files and hacksaws. As a
general
rule, however, machines must be set to run at high speed and machine
sawblades should be tungsten.
Many aluminium sections are used for office buildings, factories, shops and
other business
related sites. Aluminium sections for commercial fabrication would be
used to make items such as:
Below are some examples of different sections which make up
Aluminium shopfronts
Like all products in the construction industry, aluminium frames, windows
and doors must comply with Australian Standards. These standards are
regulations all workplaces and their workers must follow to ensure quality
products and safe work conditions. The relevant standards for aluminium
used in residential windows and doors are as follows.
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AS 4055 Wind loads for housing
AS 2047.1 Windows in buildings – specifications for materials and
performance
AS 1107.2 SAA Loading Code – Wind Loads
AS 1664 SAA Aluminium Structure Code
AS 4420 Series window tests
AS 4284 Testing of building facades
Aluminium is used extensively in the construction industry because of its:
 appearance
 corrosion resistance
 formability
 finishing variations
 high strength to weight ratio.
Shopfitting uses aluminium for a variety of applications. Uses include:
 internal fitments eg partitions and show cases
 trims such as ducted skirtings
 shopfronts.
Finishes on aluminium:
Aluminium comes in a range of finishes.
The standard finish is mill finish. This finish is the natural surface finish
achieved when the material is forced through the extrusion process. The
surface of the material is a clear aluminium finish showing die marks.
Aluminium extrusion can have three different finishes applied.
1. Chemical brightening.
2. electrochemical colouring known as anodising
3. applied finishes such as powder coating and spray painting
4. mechanical finishes such as buffing and scratch finishes.
Chemical finishes:
Include etching and bright-dipping process.
Etching process is a chemical process to give a finish of silvery white and
frosted appearance. This is done by applying a caustic solution to the
aluminium surface. The aluminium profile is passed through a hot bath,
rinsed, and then immersed in a chemical bath that removes undissolved
alloy and other surface impurities. The process is completed by further
rinses.
Bright dipping process is a specialized kind of chemical-finishing that
yields a bright, mirror-like finish. The profile is first polished and then
anodized to both protect the surface and apply desired color. Aluminium
can be bright dipped without being first polished. This reduces the cost of
achieving a bright appearance. But for that special finish the extrusion
should be polished first.
For more in formation follow the link: chemical finishes
Anodising:
Is an electrochemical process that thickens and toughens the naturally
occurring protective oxide layer on the surface of aluminium. The tough
finish is the second hardest substance known to man, second only to
diamond, but because the layer is thin it can be scratched through by sharp
protrusions. The anodic coating is part of the metal, but has a porous
structure which allows the different dyes to soak into the surface producing
coloured anodizing. Take care as the colour can be easily washed out if it
comes in to contact with caustic material that included cement and lime
products as well as dishwasher detergents.
For more in formation follow the link: Anodised aluminium
Powder coating and painting:
Paints and lacquers may be applied by brushing, rolling, pouring, flow
coating, airless or hot spraying, electrostatic coating with liquid or powder,
or immersion.
The method chosen depends upon the needs and requirements for efficiency,
appearance, uniformity of the coating, and extrusion shape. Single coat
finishes are used for decorative purposes in items that need to withstand on
little stress or human interaction and only mild chemical contacts. Multi-coat
finishes are best used for exposure to moisture, aggressive chemicals or high
mechanical stresses.
For more information follow the link: Coatings
Mechanical finishes:
This includes polishing and brushing. These techniques remove surface
imperfections and produce a uniform appearance and allow for additional
treatment in order to attain various finishes for decorative purposes.
For more information follow the link: Mechanical finishes
Joining aluminium sections
Before joining aluminium there are some important processes you will need
to follow before
joining the sections. They are processes that deal with:
 quality assurance- sizes are correct etc. all sections are available
 OH&S issues PPE and duty of care
 any special protective equipment that may be used fro material and
personal
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selecting and checking the tools for the job. Tools sharp and set up
properly
 types of aluminium sections. Are profiles compatable.
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Now that you know how to identify the correct sections and their uses,
you will need to know how to join these sections.
Mitre joints
Mitred bull joints are used to construct corners of sashes, flywire screens
and security screens. They are cut at 45° and are held together by a corner
stake internally.
Mitre cutting of corner joints offers a number of advantages, including
simplicity of preparation and neat appearance. The accuracy of the mitre
cut can only be achieved with first class sawing equipment including
facilities for clamping the workpiece during cutting. Some form of corner
stake is necessary to keep the joint in alignment.
Fitting mitre joints
Mitre joints can be secured a number of ways, including:
 serrated stakes
 pop rivets
 dimpling
 screws.
The serrated stake is designed to be a driven into each section without
distorting the walls. However, care must be taken when inserting the
corner stake into the frames as misalignment can result in dinting the
aluminium section. Screw or pop rivet fastening is necessary to secure the
joint.
Sometimes small projections are provided inside the frame section which
shear off as the stake is driven. Screw or rivet fastening completes the
joint.
Serrated stake
In some cases dimpling is used to secure the joint. While this can be done
manually, a more positive result is achieved with a press operation. Stakes
for this method of jointing can be aluminium, nylon or a plastic material
specially designed with recesses that accept the dimpling and force the
connection into a tight joint.
The mitre joint can be secured by screws where flutes are provided in the
frame section. This is most effective where the frame is firmly set around
the base material, such as fitting glass in a sash. Where the frame is not
supported or restrained there is a tendency for the joint to ride up as the
screw is tightened and all clearances taken up, resulting in an untidy joint.
Socket joint
This joint is made up of plain channel or box extrusions which have no
provisions for other forms of assembly. A spigot is fixed to one member
and the joint is completed by fixing the other member to the spigot.
Socket Joint
Mortice and tenons
The members are machined to provide holes and tenons in corresponding
positions. The tenon is riveted over after assembly. This method is used to
frame sections under 50 mm and grille fabrication.
Mortise and tenon joints
Screw and Spline joint
Screw grooves and self-tapping screws are most commonly used for
corner jointing and provide economical, secure and reliable fastening. The
advantages are that the joints can be assembled quickly and pulled up
tight. The end profiles are punched, milled or notched to provide a well
matched
joint.
Screw and spline
Besides normal strainless steel raised head screws, bolts and nuts, and a
variety of self-tapping screws are commonly used in aluminium
constructions. This type of screws are often very useful in assemblies with
extruded profiles.
From left to right:
 Sheet screw with fixed washer
 Facade screw with sealing element
 Self-locking screw with flange
 Slotted round-head screw
 Hexagonal-recess screw with shallow head
 Cylindrical self-tapping screw with flange
 Cross-head stud screw
Snap-in assembly
Aluminium products are designed and developed to finished product
standards. This means that any attachments or other sections or fittings
must use continuous extruded flutes without visible fixings. Designs are
such that the article snaps over a lug and clips into its final position.
Snap in assemblies
More information regarding the joining of Alumimium can be found at:
Joining
Preparing for joining
As previously explained, it is important you work in a safe environment
for the health and well being of everyone in your workplace. For this
reason it is essential to wear appropriate safety clothing and equipment.
You must follow all company requirements concerning protective
equipment. These requirements might include wearing:
protected hair
Safety glasses
Hearing protection
No rings or watches
No loose cuffs
Steel capped work
shoes
When cutting
aluminium always
wear a full face
shield
There are a number of different ways of preparing aluminium sections for
joining. They include:
 cutting to length - Components must be cut accurately to length after
frame clearances have been allowed.
 drilling holes - Holes are accurately marked out to take assembly
screws.
 punching holes - Machines are set up to accurately punch holes for
assembly screws. This method is generally quicker than drilling.
 cutting for joint - Some sections may have to be cut specially prior to
jointing to allow for other components of a frame. For example,
sashes
and doors to fit frames.
 trimming for fit. - Beads and adaptors may require
trimming prior to fitting.
Tools
The tools you use will depend on the job requirements and the process you
are using. Some of the tools you would use include:
to cutting
ng saw
preparation and fabrication processes
Some of these more complex tools and equipment are pictured below.
Aluminium, cut off saw with
extension table and stops
Securing joins
Two of the more common joints used in fabrication are the screw joint and
the spigot joint.
Screw joints are commonly used in frame fabrication, whilst spigot joints
are used in door and window fabrication.
Prior to assembly sealant is applied to the abutting surfaces of the joint.
This makes it waterproof.
Self-tapping stainless steel screws are used to avoid corrosion.
Spring pins
Spigot
Door stile
Door rail
S.S. Screw
Before assembling section of a frame, you must
Measure sections according to job requirements. Components must
be cut accurately to length after frame clearances have been
allowed.
§ Select the appropriate aluminium sections. Aluminium sections
cannot be forced to fit other sections If the sections do not fit
together as designed, bruising may appear.
§ Set out the aluminium sections. Setting out prior to cutting will
determine:
- cutting size of each section
- assembly sequence
- machine operations
- jointing methods.
Setting out prior to cutting components for fabrication is determined by
the different sections that will be used in its final construction.
You must consider the following factors that can determine section
lengths.
§ An assembly sequence is required so that you know which sections
are to run through and which sections run between. This will help
you to develop a cutting list.
§ Which jointing methods you use will determines how the
aluminium will be cut. This will also affect the cutting list.
§ How aluminium sections are cut to length and prepared for jointing.
This can alter the section lengths if they are filed or shaped to fit.
Remember to use your personal protective equipment when cutting and to
clean off any excess lubricant with a soft clean cloth.
§ Prepare the aluminium sections for jointing. Depending on the
jointing method, all surfaces must finish flush and without twist.
Jigs and templates will help you achieve this.
A jig can be made from an off-cut ofsection that is to butt into another
section.
The off-cut is aligned into position and the holes are marked where the
screws are to go.
Electric drill
Off cut jig –
from sill or
transom
Mullion piece
Securing the joins
After joining sections, the next step is to make sure the joins do not
separate.
When drilling for self-tapping screws, care must be taken in selecting the
correct sized hole to ensure the screw has maximum holding strength.
If spigots on corner stakes are required to join frames together, a screw or
pop rivet fastening is necessary to secure the joint.
Where joints must be waterproof, as is the case in windows and doors, it is
good practice to apply joint sealant to the abutting surfaces just prior to
final assembly. It is important that the surfaces be thoroughly cleaned of
all dirt and cutting oil, as this will prevent the sealant from sticking.
Seal the joint with
silicone or other sealer
before inserting the
screws.
Metal threads are used mainly for securing replaceable hardware items
such as:
§ locks
§ pull handles
§ door closers
§ hinges.
They are applied into tapped holes and provide excellent fixing where
permanence of thread is required for subsequent re-use.
Where heavy forces are likely to be encountered resulting in pullout
because of thread stripping, it is necessary to provide reinforcing backing
plates to increase the threaded thickness to a minimum of 6 mm.
Pop rivets enable you to attach two items together without having access to
the back side of the item. For this reason, they are sometimes called "blind
rivets".
POP - Rivets
They come in different lengths and diameters. Most rivets are aluminum,
but it's possible to also get steel, stainless steel and other metal rivets.
A pop rivet has a pin up the centre that goes into the pop rivet gun. The gun
grabs hold of the pin and tries to pull it through the rivet body. As this is
done, the head of the center pin bends out the body and crimps it tight.
When done, the center pin breaks off.
When using pop rivets, the rivet should be a snug fit in the hole through the
material. The length of the rivet should be such that before crimping, it's
sticking out the blind side about 6mm. If using rivets on soft material, you
should use a washer on the blind side to spread out the load (there are
special washers for this).
There are a range of different head types to suite most finishes. Aluminium
heads can be annodised to match the finish on the aluminium section being
used.
Steps involved in inserting pop rivets:
1. Select the right size drill
bit and drill the hole
3. insert rivet in hole making
sure it penetrates both
pieces.
2. insert the rivet into the
rivet gun.
4. squeeze the gun until the
pin “pops” off.
Pnuematic guns are available to assist the riveting process.
For more information relating to rivets go to: Blind POP Rivets
Cleaning tools
To maintain tools in their best condition, it is important that you clean
them after use. Dirty hand or power tools can affect the quality of the job.
Storing tools
As blades and cutters used to cut aluminium are usually tungsten-carbide,
it is important to store them safely as the slightest knock can damage teeth
and result in uneven cutting.
Cleaning the work area of all waste material
§ Rack longer off-cuts neatly and safely to prevent them toppling
over and causing a possible hazard.
§ All small off-cuts should be cleared from machines and
workbenches so the workplace is left clean and safe.
§ As aluminium can be recycled, all off-cuts should be placed in
containers labelled ‘Aluminium Only’.