Expanded metal mesh products are manufactured from materials that conform to the following standards:
All references to sheet size, strand width, thickness and mass are approximate. Every effort has been made to ensure these figures are accurate however the manufacturing process is subject to standard tolerances.
The finished length of an expanded metal sheet of mesh has a length tolerance that can usually be controlled with the number of finished blows per sheet. As such the length can normally be controlled to within 1 or 2 complete pattern blows. This means that it is also dependant on the mesh SWM (Short Way Measurement) and varies with the pattern profile selected. We normally ensure that the finished sheets have a '+' tolerance in the overall height (SWM direction). Generally +50 / -0 for larger mesh patterns and +25 / -0 for smaller mesh patterns (Based on standard length sheets up to 2400mm long).
The finished width of an expanded metal sheet of mesh has a width tolerance that is normally based on the raw material sheet width that is fed into our expanding machine. Note that the width is not expanded, and remains the same size as before the raw sheet is expanded. This tolerance is usually based on the tolerance of the sheets that the steel mills supply to us (often +30 / -0). Note also that most mild steel sheets are supplied to us based on imperial measurements eg 4 foot x 8 foot sizes (1220mm x 2440mm). These widths are normally left untrimmed, unless specifically requested.
The nature of the manufacturing process means expanded metal sheets have a degree of out of squareness. The tolerance for out of square is a maximum of 5mm per 1 metre of length, or 10mm per square metre on the diagonals. These tolerances are for both standard stock and made-to-order sizes. Sheets can be re-squared by guillotining/shearing on all sides, however this may result in the diamond pattern not being uniform around the edges of the sheet (varying open diamond edges).
Camber refers to the bow in a sheet. It is measured by placing a straight edge along the concave side of the sheet parallel to sheet LWM, touching both ends of the sheet. The maximum distance between the edge of the expanded metal and the straight edge is the camber. The tolerance for standard expanded mesh is 5mm per 1 metre of length.