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Grind Evolution: The Next Step in Performance Improvement

Ironwood Utility with carp leather sheath , Ironwood Utility

Grind Evolution: The Next Step in Performance Improvement

Published in Knives Illustrated Magazine (™), December 2004 issue.

Throughout history, mankind has strived to improve the way we perform particular tasks. This is evident in the products and technology around us, ranging from the very simple to the highly complex. I am not speaking of the equipment one can use to make such improvements, but of design changes that can significantly affect performance. For knife makers, one of these important design choices lies in the grind lines.

In certain time periods, a particular style of grinding was most favored. In the Stone Age, early man practiced flint knapping. During the medieval period, convex grinding was common. In the 1900s, European craftsmen focused on hollow grinds. Today, we can draw from all these traditions to create unique blades.

While obvious choices in steel selection, knife design, and heat treatment are major factors in a knife’s performance, grind lines are not often given the same attention. Many do not consider how much a certain grind line can impact the overall strength and function of a blade.

Grind Evolution Diagram
Diagram #1 and #2: Grind Evolution

Let’s compare a few common grinding styles (Diagram #1) from a metallurgical, stress–ductility standpoint and from edge geometry. For this article, we define stress as a load applied to the blade by bending it sideways.

Wherever there is a sharp shoulder or square cut, there is a potential weak point under stress. This happens because the grain flow of the metal has been cut into and left exposed.

  • Figure A: The Regular Flat Grind, found on most blades, has a weak junction where horizontal and vertical grinds meet in the plunge area. If the blade is flexed, it is most likely to break at this junction.
  • Figure B: The Modified Flat Grind adds a slight radius where the grinds meet. This radius softens the stress point, but the blade can still break at or near this junction.
  • Figure C: The Hollow Grind reacts much the same under stress as the flat grinds, even with a radius at the junction.
  • Figure D: The Sweeping Flat Grind is the strongest of all. Instead of a sharp plunge, the grind flows in a continuous curve from plunge to tip. This arch distributes stress more evenly, allowing the grind to flex like a spring, making the blade stronger overall.

To further explain the benefits of different grinds, let’s examine the parts of the cutting edge most often used:

  • The tip is used for delicate tasks or puncturing and should be strong and sharp.
  • The front third of the belly handles lighter slicing and skinning cuts.
  • The middle section is for heavier slicing and chopping.
  • The rear section is used to start tough cuts, such as whittling or cutting rope.

Most blades are ground with a uniform edge thickness from tip to plunge cut. While this works reasonably well for many tasks, it can be greatly improved. Looking at the exaggerated edge drawing (Diagram #2), it is clear how a sweeping grind line provides significant benefits. The blade is stronger, with finer geometry at the tip and belly for precision cuts, and more thickness at the base for heavy-duty use. A sweeping flat grind is not only graceful and aesthetically pleasing, but also mechanically superior.

What would you rather own: a sports car with wagon wheels, or one equipped with performance tires?

Written by Thomas Haslinger