The blade heel is a challenge

[uilleann]

I have posted before about the interference of the bolster or plunge at the heel of the blade.  I think I have worked around most of that by taking the blade out of my folders and sharpening with just that.  The added bonus is that it offers me a knife flat for a true vertical alignment.

And I have been getting very sharp mirror finish edges that I like.

 

https://youtu.be/ezwGgZdEBzo

But…. the heel is always a bit less sharp and a bit less mirrory.   I think at every grit level the back 1/4-3/8″ is always rougher than the rest of the blade.  I have tried to be gentle with the stones and moving them in all directions to reduce the grind marks.  And it always make that area better but not great.

In the end that area will be sharp, but not as sharp as the rest of the blade.  And at first glance have a mirror edge but upon closer examination it will have faint grind lines.

I noticed the same problem when I used the KME system.

Any thoughts on how to improve this?

[Organic]

The blade in the video looked great!</p>

The only thing I can suggest is to be unaffraid to move back down to a more coarse grit when you notice the problem. It takes extra time, but if the imperfections bother you I think you’ll thank yourself for spending the extra time to get it right.

 

Also, with the coarse grits it is a good idea to avoid horizontal strokes or motions. These have been shown to cause micro chips at the apex that are very difficult to remove and leave the edge with a jagged feel.

[uilleann]

Just did another blade and I think I discovered part of my problem.  I do scrubbing up and down moves first along the blade which puts vertical or slightly angled grind lines on the blade.  Then I have been doing the long stropping kind of strokes which take out 95% if the vertical grind and live a lighter 45 degree-ish grind marks from heel to tip.

Here is where I made my discovery.  When i do the stroke movements I have been going mostly down at the heel and then turning to follow the blade after that.  So I was kind of leaving the first vertical grind marks.   Today I made a  slow and deliberated effort to not go down but go more towards the tip than down.  I also would come back and do very light mico- movements of a 1/4 to 1/2 and inch to make sure that I was changing down grinds to 45 degree grinds.

Seemed to work pretty good on todays blade.  The heel was an order of magnitude better on less scratches there.

[tcmeyer]

One of the “cons” of the Wicked Edge is related to the relative motion of the stones at the heel.  The amount of steel removed at any point on the edge is a function of the linear inches of abrasive passing over that point fro each stroke.  Consider a point in the mid-point of the edge.  If you are using scrubbing strokes, a 3/4″-wide stone typically passes that point twice for each “back and forth” stroke.  A horizontal stroke produces 1.5″ of abrasive passing over that point for each stroke.  A 45-degree stroke (up or down) produces about 2.12″ of abrasive passing over that point.  An 80-degree stroke produces almost four full inches of abrasive passing by.  At the very end of the bevel, where the edge meets the ricasso, there is almost no linear amount of abrasive passing by if the stroke is anything but vertical.  In fact, between the ricasso and 3/4″ toward the tip (the width of the stone), the amount of abrasive passing any one point will be a variable dependent on the angle.  At the ricasso, the linear displacement is zero and at the 3/4″ point it will be the full extent of displacement dependent on the angle of the stroke.  Between the two points, the displacement will be a proportion dependent on the distance from the ricasso.  With 45-degree strokes, the abrasive displacement at 3/8″ will be about 1.06″.  At 3/4″ the displacement will be the full 2.12″ but at the end (the last bit of edge at the ricasso) it will still be zero.

The end result of this is that you’ll see a clear difference in the polish pattern in that last 3/4″.  If you try to compensate by taking some vertical strokes with the stones up against the ricasso, the resulting pattern will be a very obvious 3/4″-wide track.  This is caused by the fact that the downstream edge of the stone follows the edge which is riding against the exposed ricasso.  I try to eliminate this by starting my strokes with the stone against the ricasso, but then starting my stroke vertically, and then arcing forward and away from the ricasso.  With practice, you can blend the abrasive pattern into the main bevel.

If I haven’t made myself clear, please let me know and I’ll try again.  Or better yet, one of our advanced users can step in and straighten us both out.  I know there’s at least a couple here who are smarter than me.

7 users thanked author for this post.

sksharp, ArrSea Defense, wickededge, Organic, Marc H, Mark76, uilleann

[uilleann]

Good explanation, thanks.   But any interest in doing a video of that movement…. or have you seen that technique in other videos?

[wickededge]

tcmeyer’s explanation is exactly right.

-Clay

1 user thanked author for this post.

tcmeyer

[sksharp]

Great explanation TC, I had to read it twice to get it all, I don’t think I’m one of those smarter guys you referred too.

After a lot of reading and listening to several of the experienced folks on here I have started using a edge leading stoke and have found that what TC explained is exactly right and if you start at the heel and make sure you start down before forward that it is MUCH easier to blend the full length of the bevel. With edge trailing strokes I just had a very hard time blending it all together. I could not have explained that nearly as well as you did TC. THANKS

2 users thanked author for this post.

Dwight Glass, tcmeyer

[Author]

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