Innovation - Function - Design
Grind Evolution: The Next Step in Performance Improvement
Published inKnives Illustrated Magazine (™), December 2004 issue. Throughout history, mankind strove to improve the way we did a particular task. This is clearly evident in the products and technology around us, ranging from very simple to quite complex tasks. I am not speaking of the equipment one can use to make such improvements; but of simple design changes which have a big impact on a product’s performance. For knife makers, one of these design changes is in the grind lines.
In certain time periods, a particular style of grinding was the most favored. In the stone age, early man did flint napping, medieval man worked on convex grinding and in the 1900’s, the European man focused on hollow grinds. Today, we can choose from the grinding styles that came before us to make a unique blade.
While obvious choices in the steel selection, knife design and heat treatment are major factors in the performance of a knife; grind lines are not often viewed in this way. A lot of folks do not think about what impact a certain grind line will have in the overall performance of one’s knife.
Let’s compare a few of today’s grinding styles (Diagram # 1), from a metallurgical, stress - ductility standpoint and from the edge geometry. For this article we define stress as a load applied to the blade, by bending it sideways.
Where there is a sharp shoulder or square cut, there is a possible weak point under a stressful condition. This is due to the fact that the grain flow of the particular metal has been cut into and left exposed.
- Figure A: The Regular Flat Grind, which is found on a majority of blades, has a definitive weak junction where the horizontal and vertical grinds meet in the plunge area. If the blade should be stressed by flexing, it is most likely to break at this junction.
- Figure B: The Modified Flat Grind has a light radius where the grinds meet. This radius acts as a buffer, but still the blade will break at or near the grind junctions if it is subject to stress.
- Figure C: The Hollow Grind will act the same to stress as the above flat grind blades, even with a radius grind junction.
- Figure D: The Sweeping Flat Grind, to date, is the best grind of them all. Why? The grind sweeps in a gradual arch from the plunge, (which is not a true plunge any more) to the tip. Because of this arch, the grind will act like a spring should the blade get flexed under stress and there fore it is much stronger.
To further explain the benefits of a particular grind, we should examine the areas along the cutting edge that are used during cutting tasks.
- The tip of the blade is mostly used for delicate tasks or puncturing and should be strong and sharp.
- The front 1/3 of the edge’s belly gets used for lighter slicing and skinning cuts.
- The mid section of the blade’s edge is used for heavier pressure slicing or chopping.
- The rear section is used mostly to start a heavier cut; as in whittling, cutting rope and (or) chopping.
Most blades on the market are ground with a uniform edge thickness from tip to plunge cut. In general, this is a good grind and does most tasks required, it can be greatly improved on. Now look at the exaggerated drawing of the edge in Diagram # 2. A knowledgeable user can clearly see the benefits of such a sweeping grind line. The blade is stronger, while the edge geometry is delicate where it needs to be and more meaty for the heavier use areas. The sweeping flat grind is ascetically pleasing as it follows the shape of the blade gracefully. But make no mistake, it does so much more than be pretty. What would you rather own, a sports car with a set of wagon wheels or one with a set of performance tires?