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The Best Material in Manufacturing Superior Knives

Changing material is by far the easiest way to increase the useful lives of your knives. Extending the life of a cutting edge by three-five times by changing the material is not uncommon. In one case, 0-1 knives lasted six hours slitting rubber for golf ball thread, whereas M-3 high speed knives ran over a month before regrinding was necessary. While the M-3 knives were three times as expensive as the 0-1, the regrinding costs were only slightly higher and the total benefits more than justified the extra cost.

Material specifications are as important in establishing the durability of the tool as dimensions are. Our experts at Florida Knife will help you select which of the 100 grades of tool steel recognized as standard by the AISI would be best for your needs.

  • Table A below gives a list of some of the more common steels used in the manufacture of machine knives and a brief description of their uses.
  • Tables B and C evaluate wear resistance of the common steels.
  • Tables D compares the edge strength of various steels.
  • Table E measures the effectiveness of these steels to resist corrosion.

It should be understood that not all of the steels are available in small quantities or in all forms. Also, it may not be economically feasible to make large knives of solid carbide or high speed steel, although in some instances high speed or high alloy steels can be inlaid as a knife edge material, or carbide can be brazed to a backing of less expensive steel.

Learn about other important processes needed to create a good machine knife:

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table-a

Table A - Common Knife Steels

table-b

Table B - Wear resistance of common steels used in manufacturing machine knives

The relative wear resistance of the steels in this chart is determined by measuring weight losses after specimens were abraded by a rubber wheel and quartzite. The lower the weight loss, the higher the abrasion resistance.

In use, not all steels react exactly as shown on the list and the differences in performance are usually greater than the figures would indicate.

table-c

Table C - Wear Resistance at Elevated Temperatures

This chart compares the wear resistance of steels and carbide at elevated temperatures. In some operations, such as shearing steel, the material to be cut is heated to 500° to 900° F to avoid edge cracking. Often slabs and blooms are sheared to 1600° or higher. In other operations, the heat developed in use can be high enough to soften the edge of a knife that has only been tempered to 300° to 400° F.

table-d

Table D - Edge strength of steels commonly used in manufacturing machine knives

For some operations, it is necessary to sacrifice abrasion resistance for edge strength. For example, D-2 knives would last many times longer than A-8 for brush chipping except that often stones or nails are thrown in the chute with the tree branches. A-8 can withstand much more of this abuse, while D-2 would tend to break. Other steels used where strength is needed are L-6, S-1 and S-5, which have silicon or nickel added to increase toughness. Another alternative is to reduce the hardness which will increase toughness. This chart compares the shock resistance of various steels.

table-e

Table E - Materials that will resist corrosion

The edges of some of the hardest materials can be quickly eroded by acid in the materials being cut. Tungsten carbide, so hard that it is usually ground with diamond wheels, will not last long at all around acids, as they eat out the cobalt binder, causing the cutting edge to flake off. Even in cutting rubber, the sulfur combines with the water coolant to form a mild sulfuric acid which will pit and corrode a knife's cutting edge.

Any of the steels with a chrome content over 4% will effectively resist corrosion in varying degrees, with 440-C Stainless being the best.