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How to measure and specify expanded metal

How to measure and specify expanded metal

Our customers sometimes find themselves confused over what measurements they should provide in order to select the most suitable mesh pattern for their application. Ian Hutchinson, Product Manager at The Expanded Metal Company, provides a guide on how to measure and specify expanded metal…

 

Raised or flattened mesh, what is the difference?

When measuring expanded metal mesh, the first thing to consider is whether the mesh is raised or flattened.  Both have a unique set of terminologies with regard to their respective measurements.

The original form of expanded metal is always of a raised appearance and is characteristic of the unique ‘slit and stretch’ motion employed to manufacture the product. which presents angular strands which are inclined from the plane of the sheet. 

Raised mesh is championed for its angular appearance which not only gives it strong aesthetic appeal but offers practical benefits: it offers grip underfoot, has the ability to direct air, liquid and light, and provides a key when used as a substrate.

Common applications for raised mesh include walkway ramps, security fencing, decorative building cladding for interiors and exteriors and laths for render and plaster.

A secondary process is often applied to expanded metal which utilises heavy rolls to flatten the angular strands.  The end result is a sheet which is completely two dimensional with its strands in the same plane as the sheet. Flattened mesh is often championed when a flush finish is required.

Common applications for flattened meshes include security partition meshes, conical air filters and machine guards.

How do I measure a raised mesh?

The key measurements for a raised mesh are Longway Pitch (LWP), Shortway Pitch (SWP), Strand Width (SWDT) and Strand Thickness (STK).

LWP, measured horizontally from either knuckle to knuckle or centre to centre, is derived from the size of tooling used within the production process.

SWP, measured vertically from either knuckle to knuckle or centre to centre, is manifested through the overall expansion applied during manufacture.

SWDT is a measurement of the width of the resulting angular strand created during manufacture.

STK, is a measurement of starting raw material thickness.  Contrary to belief, the expanding process does not directly alter material thickness. Strand Thickness should not be confused with the overall height or depth of expanded metal. Typically, mesh height can be as much as 1-2x the measurement of SWDT.

 

How do I measure a flattened mesh?

The key measurements for a flattened mesh are Longway Aperture (LWA), Shortway Aperture (SWA), Strand Width (SWDT) and Strand Thickness (STK).

LWA is measured horizontally from internal aperture point to point.

SWA is measured vertically from internal aperture point to point.

SWDT is a measurement of the width of the resulting angular strand created during manufacture.

STK is a measurement of starting raw material thickness. 

Whilst the expanding process does not alter material thickness, the flattening process does.  It is common to observe a 10-20% reduction in material thickness after the flattening process.  As the mesh is completely two dimensional after flattening, the overall height measurement of the mesh is akin to starting material thickness with a further allowance of 10-20% reduction.

How do I specify sheet size and orientation?

Expanded metal mesh exhibits different mechanical and aesthetic properties when the sheet size is orientated at opposing angles. 

When specifying sheet dimensions, one should also consider the orientation of the diamonds in relation to sheet size.  The terminology employed to describe orientation is Longway Mesh (LWM) and Shortway Mesh (SWM).

For example, when raised mesh is used as a walkway ramp platform, the surface grip is strongest when the diamonds run left-to-right underfoot.

Alternatively, it is common within the security fencing industry to mount expanded mesh fencing panels with the diamonds longways pointing to the sky.  This creates narrower openings and inhibits the ability to climb and scale the fence.

The below illustration provides a clear explanation on how 2440mm LW x 1220mm SW differs to 1220mm LW x 2440mm SW despite being dimensionally the same.

View an example of our 2076F flattened steel mesh at a horizontal orientation here and view the same mesh at a vertical orientation here. 

You can also view our 2089 raised steel mesh at a horizontal orientation here and at a vertical orientation here

For more support and to discuss your requirements further call us on 01429 867388 or email sales@exmesh.co.uk