Hardness & Toughness

Industrial knives are generally used to shred, cut and grind a vast quantity of materials which can range from textiles, rubbers, plastics, metals, WEEE recyclables and wood, industrial knives and blades are used to reduce the size and process all kinds of materials as stated above. Because of the wide variety of applications leading to very diverse stresses on the blades, a variety of knife materials must be used to achieve the needed results while also providing long durability for the knife-edge or blade.

The characteristics we try to achieve for our industrial knives and blades are a combination of edge holding capability or “wear resistance” combined with toughness. The perfect industrial knives and blades would be ones that would hold its edge indefinitely combined with one that could take severe stresses and not break. There are no universally accepted measures for either of these characteristics, but the industry has developed a couple of assessable methods that give us guidance and insight into evaluating the functionality of industrial knives.

Hardness

There are a variety of scientific measures of the hardness of materials, but for purposes of industrial knives, the one that is the most widely accepted is the Rockwell C scale. While not being the most perfect way to measure resistance to wear, the rate of wear of industrial knives and blades correspond well with this measure. To summarise this rating system, the harder the Rockwell rating for given knives and blades, the more wear life or wear resistance the knives and blades should display. It should be taken into consideration that if other sources of wear are involved besides friction, the Rockwell C scale system may not give good guidance. An example of this situation could be in a chemical environment where chemical erosion may be the primary cause of knife and blade wear.

Toughness

With measuring the toughness, there are no clear or precise methods of this for industrial knives and blades. One of the best measures to give guidance and some insight into this regard is Transverse Rupture Strength. This measurement system only gives you somewhat of insight, but the idea behind this is the higher the TRS reading, the tougher the knives or blades are likely to be. There are other measurement methods that also give guidance for example Young’s modulus of elasticity, but for general applications, the TRS reading gives the best and easiest guidance.

Hardness and Transverse Rupture Strength are usually reverted proportionally. As the material is made harder, it will tend to become more brittle giving it a lower TRS.

To deal with this issue, different materials that have different wear characteristics and toughness characteristics can be used to get different performance criteria. Changing materials for example to something such as stainless steel can help combat chemical erosion as it’s a resistant material. Bear in mind that while it may seem logical to use the material with the best combination of wear and toughness characteristics for every application, materials that fit that description tend to be more expensive and so cost becomes a factor so get in contact with our design team they can help you design knives or blades and will assist with configuration and recommend material that will give you the best solution and prices for your machines. 

Other aspects to consider include edge preparation, coatings, plating and other material enhancement processes.