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Post subject: Adv Sharpening Series: Zero Grind Edges M390
Posted: Thu Nov 15, 2012 7:51 am
Joined: Mon Apr 23, 2012 4:45 am Posts: 1672
Advanced Knife Sharpening Series: Zero Grind Edges Using Diamond Belts on M390
In this video I demonstrate converting a flat grind bevel to a zero grind. I'm using a Coote Belt Grinder with a variable speed motor and a forward and revers footpedal. This setup is described in more detail in a previous video.
First I review various regions of the belt - the top pulley, the lower 10" contact wheel, the platen and the slack portion of the belt. I focus on the region to either side of the platen and demonstrate how these various regions have differing degrees of flexibility from the middle of the slack area to the area to either side of the pulley.
The knife used for this demonstration is the Richmond Artifex. This knife uses a very abrasion resistant steel, M390.
While the original angle on the knife is quite reasonable, I'm a bit more extreme in terms of putting ultra high performance edges on knives, so I'm going to convert this edge to a zero grind edge. What this means is that the two sides of the knife will be meeting with no separate bevel and only a slight convex grind on the edge of the knife.
Please note that this sort of a grind is not easy or even possible to make with a poor quality steel. As you will see in this demo, this knife has absolutely NO problem taking this acute of an edge, showing itself to be a remarkable steel and heat treatment!!
To perform this tasks, I'm going to be using diamond belts, which work remarkably well on these abrasion resistant steels.
The material that these belts are made of I also have available mounted on glass for the EdgePro, 1x6" 2x6" Wicked Edge to fit the standard paddles and as bench strops in 3x8" size to fit standard stone holders. Please note that I am not using water cooling in this video and at the speeds I am using generating almost no heat buildup as these belts run very cool. When using these belts as bench 'stones' or strops, I do use water as one would with diamond lapping plates or waterstones.
The first belt is a 125 micron belt - approximately 120 grit. I run the grinder at approximately 1000 RPM.
Using my leather gloved hand as a platen for support in the slack portion of the belt I begin grinding away the bevel, including the area behind the bevel. This is essentially thinning the knife and knife edge until no bevel remains with a slight concavity imparted by the 'give' in my hand being used for support to produce a convex edge. I continue, taking advantage of the area immediately in front of the platen to grind a more acute convex bevel. I repeat this procedure on the opposite side. Note especially near the tip how long I can remain in contact with the blade without overheating the blade which stays cool throughout the procedure.
The diamond belts cut through the M390 'like'butter' with little more effort than more ordinary abrasion resistant steels.
Next I switch to a 74 micron belt to refine the edge and work on the entire surface with this belt, avoiding the logo using the technique mentioned in an earlier video.
I develop some burr with this belt and demonstrate deburring by abrading it off using LIGHT pressure. Note the sound decreased using lighter pressure.
Next I go to 45 micron belt, continuing to refine the edge. The knife will be further refined to 9 microns on the grinder and finished using hand sharpening techniques.
The M390 Artifex is available at Chefknivestogo. For more information about the diamond film products including bench strops or plates and films mounted for use on both the EdgePro and Wicked Edge, contact me directly.
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