{"id":9467,"date":"2026-08-14T10:49:44","date_gmt":"2026-08-14T03:49:44","guid":{"rendered":"https:\/\/giaanh.vn\/?post_type=kien-thuc&p=9467"},"modified":"2026-10-15T09:16:10","modified_gmt":"2026-10-15T02:16:10","slug":"part-3-tolerances-and-how-to-measure-them-correctly","status":"publish","type":"kien-thuc","link":"https:\/\/giaanh.vn\/en\/knowledge\/material-tolerances-and-measurement-methods-for-acceptance-inspection\/","title":{"rendered":"Part 3: Material tolerances and measurement methods for acceptance inspection"},"content":{"rendered":"

Two parties may measure the same steel plate using the same type of measuring tool and still reach different acceptance inspection conclusions. The reason may not lie in the material quality itself, but in differences in the measurement position, distance from the edge, measurement length or plate support conditions<\/strong>.<\/p>\n

For industrial steel plate, tolerances need to be evaluated according to the applicable standard and the agreed tolerance class. If a measurement record contains only the final result without documenting the measurement conditions, it can be difficult to determine whether the difference originates from the material or from the measurement method.<\/p>\n

The acceptance inspection process should therefore begin by defining the tolerance requirements, agreeing on the measurement method and recording the measurement conditions in full<\/strong>.<\/p>\n

1. Material tolerances need to be evaluated according to the correct standard<\/span><\/h2>\n

Tolerance is the permitted deviation from the nominal dimensions or geometry of a product.<\/p>\n

For hot-rolled steel plate, two standards need to be distinguished: EN 10029 and EN 10051<\/strong>.<\/p>\n\n\n\n\n\n\n
Standard<\/th>\nScope<\/th>\nItems to inspect<\/th>\n<\/tr>\n<\/thead>\n
EN 10029<\/td>\nHot-rolled steel plate within the scope of the standard<\/td>\nThickness tolerance, flatness, squareness and related dimensional requirements<\/td>\n<\/tr>\n
EN 10051<\/td>\nContinuously hot-rolled flat products and products cut from coil within the scope of the standard<\/td>\nDimensional and geometrical tolerances applicable to the relevant product group<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

These two standards should not be used interchangeably when the products do not fall within the same scope.<\/p>\n

An important point is that tolerance is not defined by a single level<\/strong>. Dimensional and geometrical requirements are divided into different levels or classes specified by the applicable standard.<\/p>\n

When purchasing material, the appropriate tolerance class should therefore be selected according to the intended use rather than assuming that the product will automatically be supplied to the most stringent tolerance level.<\/p>\n

2. The tolerance class needs to be selected before ordering<\/span><\/h2>\n

Not every component requires the same level of dimensional accuracy and flatness.<\/p>\n

For example, a steel plate used as a substrate for installing a ceramic lining may require greater flatness than a plate used for certain conventional welded structures.<\/p>\n

If the substrate is not sufficiently flat, the adhesive layer may become uneven, creating areas where the lining is more susceptible to detachment.<\/p>\n

For load-bearing components, on the other hand, thickness deviation may affect the basis of structural calculations.<\/p>\n

Before selecting the tolerance class, the technical and quality teams need to clarify two requirements:<\/p>\n\n\n\n\n\n\n
Requirement to determine<\/th>\nBasis for tolerance selection<\/th>\n<\/tr>\n<\/thead>\n
Flatness requirement<\/td>\nFlatness required for installation, welding, machining or lining installation<\/td>\n<\/tr>\n
Thickness requirement<\/td>\nEffect of thickness deviation on finished dimensions and the component’s load-carrying capacity<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Once the application requirements have been established, the tolerance class needs to be clearly specified in the order<\/strong>.<\/p>\n

If it is not defined from the beginning, the delivered material may comply with standard tolerance requirements but still be unsuitable for the actual machining or installation requirements.<\/p>\n

The tolerance class should be selected based on the function of the component<\/strong>, rather than waiting until the material arrives at the warehouse to determine the required level of accuracy.<\/p>\n

3. A measurement record needs to document three conditions clearly<\/span><\/h2>\n

Before determining whether a plate complies with the specified tolerance, three basic conditions need to be established:<\/p>\n\n\n\n\n\n\n\n
Condition<\/th>\nInformation to record<\/th>\nSignificance for the result<\/th>\n<\/tr>\n<\/thead>\n
Applicable standard<\/td>\nStandard number, version and agreed tolerance class<\/td>\nDefines the permitted limits used for evaluation<\/td>\n<\/tr>\n
Measurement position<\/td>\nMeasurement point on the plate, distance from the edge and reference length where applicable<\/td>\nEnsures that results are generated at comparable positions<\/td>\n<\/tr>\n
Plate support conditions<\/td>\nSupporting surface and plate position during measurement<\/td>\nReduces deviations caused by unsuitable measurement conditions<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Of these three conditions, measurement position and supporting surface are particularly easy to overlook<\/strong>.<\/p>\n

If one party measures close to the edge while the other measures at the position specified by the standard, the two measurements may produce different values.<\/p>\n

Similarly, a steel plate placed on a surface that is not sufficiently flat may produce an inaccurate flatness assessment.<\/p>\n

The two results should therefore only be compared directly when the corresponding measurement conditions have been aligned<\/strong>.<\/p>\n

4. Measuring steel plate thickness during receiving inspection<\/span><\/h2>\n

Thickness is one of the properties that can be checked directly in the warehouse using suitable measuring equipment.<\/p>\n

However, the number and location of measurement points need to be clearly defined so that the results properly reflect the applicable tolerance requirements.<\/p>\n

4.1. Determining the measurement positions and number of points<\/span><\/h3>\n

Under the inspection approach used in this documentation, each plate is measured at a minimum of three points, avoiding positions too close to the edge.<\/p>\n\n\n\n\n\n\n\n\n\n
Item<\/th>\nRequirement<\/th>\n<\/tr>\n<\/thead>\n
Equipment<\/td>\nSuitable thickness measuring instrument<\/td>\n<\/tr>\n
Number of measurement points<\/td>\nAt least 3 points per plate<\/td>\n<\/tr>\n
Measurement position<\/td>\nDo not measure too close to the edge; follow the distance specified in the applicable standard<\/td>\n<\/tr>\n
Basis for evaluation<\/td>\nTolerance class specified in the order<\/td>\n<\/tr>\n
Results to retain<\/td>\nValue and location of each measurement point<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

The measurement position is important because plate thickness near the edge may differ from the internal area of the plate<\/strong>.<\/p>\n

A measurement taken too close to the edge should therefore not be used to represent the thickness of the entire plate when that position does not comply with the specified measurement method.<\/p>\n

4.2. Handling a measurement outside the tolerance<\/span><\/h3>\n

If one measurement point falls outside the specified tolerance range, the quality department should perform additional measurements and record the results.<\/p>\n

A single abnormal value should not be used immediately to reject the entire plate.<\/strong><\/p>\n

The measurement record should include:<\/p>\n