Sharpening Fillet Knives and other Flexible Blades

Sharpening Fillet Knives and other Flexible Blades

Fillet knives and other flexible blades can be sharpened in any Wicked Edge sharpener, but they do require some different sharpening techniques. The challenge these types of blades present are: 
  1. They are flexible
  2. They can be long
  3. The blade width from spine to edge is often narrow
Using the techniques described in the video and in the text below,  you can successfully sharpen and maintain the edge on your flexible knives.

Angle Selection 

The first thing to consider when you set out to sharpen a fillet knife (or any thin, flexible blade) is angle selection. Flexible blades are not made from extremely hard steels; in order to maximize flexibility, knife manufacturers manage their heat treatment to optimize for toughness instead of hardness. For this reason, you will want to choose a sharpening angle in the 20-25 degree range.

Edge Finish (grit)
Fillet knives are generally used with a draw-cut, or slicing motion. For this reason your knife will be more effective if you do not polish the edge. Instead, create an edge that has very fine micro-teeth by finishing it with a 1000, 1500, or 2200 grit diamond stone. We don't recommend using Lapping Films or Leather Strops on these types of knives.

Clamping Fillet Knives (or any knife with a small blade profile)

Due to the slim blade profile of a fillet knife, you will want to clamp it as high in the vise as you can. Your target should be for the edge to reach 5/8" over the top of the vise. If you can't get to 5/8" because the blade is too small, that's okay. Just clamp it has high as you can. On a lot of fillet knives you won't be able to use the sharpener's depth settings and depth key. Without using the depth settings, repeating this blade position for your next sharpening session can be accomplished by measuring exactly how high the edge rests over the top of the vise and then recording that measurement, or you can use a Wicked Edge Advanced Alignment Guide and record the position the knife enters the guide and where the tip falls within the guide. 

Overcoming Blade Flex While You Sharpen

Flexible blades are going to deflect from side to side while you sharpen them. This small amount of movement is expected and the result may be an edge with a slightly convex (curved) profile, which is beneficial to these types of knives because it will help with edge retention. You can take measures and use some different techniques to help minimize the blade flex. 
  1. Clamp the knife closer to the tip - the most flexible part of the blade is where the blade is thinnest, which is by the tip. So, if you clamp close to the tip you can prevent it from flexing so much. 
  2. Stabilize the knife by bracing the knife's handle with your hand - When you profile (re-shape) the edge and draw a burr at the beginning of the sharpening process, you will need to use a bit of pressure with the stones. During this process you only work one side of the knife allowing you to hold the handle of the knife with you other hand, to keep it from flexing.
  3. Use very light pressure - This is key. Once you have drawn a burr from each side of the knife, start alternating your strokes and apply extremely light pressure with the stones. This is a great technique to practice and is useful for all knives you may sharpen, because you will produce sharper results with less pressure. 
  4. Use a downward-and-out (edge leading) stroke - You get more control over the blade flex when you move the stones toward the edge instead of away from it.

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