|Does the angle change along the length of longer blades on the Wicked Edge™?|
|Written by Clay Allison|
|Thursday, 16 June 2011 14:12|
There is considerable (and mostly misinformed) debate on the web about angle change on guided sharpening devices along the length of the blade. Contrary to most peoples’ intuition, the angle does not change throughout the straight length of the blade, no matter how long the blade is. It will change through the arc of the belly of the knife where the edge dips to the spine. The geometry at work is planar in nature and because the stones are able to rotate on the guide rod, they are able to maintain the same plane of contact with the blade when the blade is straight. When the blade begins to curve, the stone enters a new plane at a different angle. This new angle can be more acute or more obtuse depending on its distance from the pivot point of the guide rod. You can adjust for this effect by mounting the blade with the tip at varying distances from the clamp. Using a Sharpie marker to color in the bevel will help you quickly establish the optimum front to back positioning for your knife by allowing you to visualize the way the stone tracks along the curve. You can use the record keeper supplied with the kit to jot down the settings for each of your knives and repeat those settings for future sharpening sessions. When you’ve adjusted so that the angle is perfectly consistent throughout curvature of the blade, you may have a slightly wider bevel at the tip because the edge is being cut from the thicker stock of the blade near the spine, unless the knife has a distal taper.
Here the stone is against the ruler directly above the pivot point. The angle shown on the cube is 17.4 degrees. There is a second square behind the cube ensuring that the cube is plumb.
Here the stone is held at 5.5 out from the the pivot point, simulating an 11" blade. The Angle Cube reads 17.3 degrees. The square is again behind the cube keeping it plumb. The margin of error on the experiment was ±.1 degree.
The image below shows the adjustment of the knife to find the "sweet spot".
I recently wrote a brief article on Blade Forums about finding the ideal location of the knife in the clamp:
This issue comes up a lot and gives people fits but it's very easy to solve. On a practical level, there are a couple of reasons why you might get a larger or smaller bevel along the curve of the blade.
|Last Updated on Friday, 29 July 2011 16:09|