ISO 13997 Cut Resistance Test

The ISO 13997 Cut Resistance Test allows you to make sure that cut-resistant personal protective equipment is fit for purpose.

Cut resistant fabrics are produced in many forms and for a variety of purposes, including clothing, shoes, gloves and even head protection. In most cases, any risk arising from serious cutting hazards should be removed from business activity - for example, by the use of guards - the operator is obliged to request protection from small knives and cutters only against relatively minor hazards.

These minor cutting hazards cannot usually be eliminated due to the nature of the job (for example, cutting operations requiring the precision and dexterity provided by hand cutting). However, although the potential damage that can be caused by cutting with a single blade is slightly less than a circular saw or laser cutter, it can still be fatal. The use of cut-resistant personal protective equipment (PPE) should therefore always be considered where there is a risk of cut.

Most minor cuts occur on the hands as these are the body parts closest to the process that normally involve a sharp blade. Other parts of the body can usually be protected by modifying the cutting practice or using additional guards, but hands (in most cases) are required to perform the cutting and therefore cannot be removed from the procedure.

Mechanically protected gloves are classified in EN 388: 2016 + A1: 2018. It is based on five characteristic protection elements: abrasion, knife cut, tear, puncture and impact resistance, each element is divided into protection levels. Similar tests on fabrics used in other types of protective clothing are carried out at minimum levels according to the expected hazards.

For gloves, the blade cut resistance is divided into five levels; level 5 is the most durable and level 0 provides the least protection. Traditionally, the level is based on the cut index gained by a test using a rotating blade pulled through fabric samples until cutting occurs. This is often called the 'impact test'. However, where fabrics have high cut resistance, this test can often produce abnormal results due to blunting of the test blade. In such cases, an alternative method specified in EN ISO 13997: 1999 is used.

The ISO 13997 method uses a straight blade that is pulled across a small piece of fabric until cutting occurs. The principle of this test is to change the load that must be applied to the blade to make it easier to cut at a known distance. Compared to the impact test, the blade only travels a short distance, which means blunting of the blade plays a much less important role.

An ISO 13997 blade cutting tester consists of a flat blade (of known sharpness) attached to a carrier and capable of horizontal movement to pull the blade across the specimen. The fabric sample is mounted on an inclined surface. In contrast, this is placed on top of an array of arms simulating a mass placed above the blade to apply a force to the blade from under the sample holder. The blade is pulled through the sample at a certain speed with the distance traveled until the cut (called 'stroke length') is recorded. Typically, the transition is indicated by the point at which an electrical contact is made between the blade and the holder. Therefore, where fabrics contain steel threads,

The testing procedure begins by performing a series of cuts using various masses applied to the blade to obtain a suitable range of cut lengths. This is typically five cuts in the 5-15mm range, five cuts in the 15-30mm range, and five cuts in the 30-50mm range (cut lengths less than 5mm or over 50mm are ignored). Using this data, a scatter plot can be drawn by plotting the stroke length relative to the applied load.
From this graph, by drawing a trend line from the data points, an estimate can be obtained for the applied load required to obtain a stroke length of 20 mm before cutting (an exponential graph usually provides a fairly good correlation). Using this estimate, the graph is redrawn and five more cut tests are performed. If the average of these five cuts is within an appropriate tolerance from 20 mm (± 2 mm), another estimate is taken from the new graph and recorded as the final result. If the mean of the five cuts is out of tolerance, the new forecast is used for the next five cuts and the results are used for a final resplan. The final estimate from this third chart then becomes the final test result. The test result is based on the estimated force required to generate a 20mm stroke length in Newtons.

The blades for this test are made to a specification determined by the test method. Each batch is checked for average sharpness by defining a sharpness correction factor. Groups of knives with too low sharpness or a large variation in sharpness are rejected. Once the blades are accepted, each batch is assigned a correction factor that is used to normalize the results of each cut test. For example, a blade sharpness correction factor of 0,5 will result in halving the length of each stroke. A new blade is used for each shear test - and discarded after use - to ensure blinding is not a major factor in results.

Although the main purpose of the ISO 13997 cut test is to provide data for comparison between fabrics (the greater the force, the higher the cut resistance), the requirements for cut resistant gloves are included in EN 388.

It is also worth noting that due to the differences in the two methods used for cut resistance, there is no correlation between the two methods - a material can reach different levels using various test methods. It's also worth noting that the methods have different benefits that make them more suitable for various types of materials. However, the ISO 13997 method is generally considered to be more accurate for high levels of cut resistance. The trade-off is that due to the need for a large number of individual cuts (each using a brand new blade) the ISO 13997 method is significantly more time consuming and costly to execute.