Uneven pressure along length of knife

[Drew]

So, I’m noticing that my ark on any given grit seems to hang up on the belly (right term? The curve after the flat, before the tip.). My thought is that more pressure means more metal removed and deeper scratches. Just double checking, but I should be ensuring an even pressure along the entirety, yeah?

Thanks y’all.

 

Sincerely,

Drew

[Marc H]

Sounds like you may need to position your knife better.  Finding the proper balance between the flat portions of the knife edge and curved portions is “the sweet spot”.  From how you describe it, (“seems to hang up on the belly”) it sounds like you may need to rotate your tip down some or move your knife back some, or both.   I agree with you, more pressure being used is because your removing more steel from that area of the blade and thus changing the shape, (i.e., profile) of the knife in that area.

Anyone can easily throw any knife in the vice and clamp it tightly, then got to work on it and eventually get a sharp edge by removing enough steel to apex the two opposites sides to a sharp edge.  It’s a bit more difficult to clamp a knife in the vice, securely, in a proper position to remove steel in just the right amounts and in just the right places to create a sharp edge without changing the shape and profile of the knife from how it was designed and originally made.

Marc
(MarcH's Rack-Its)

4 users thanked author for this post.

DaveG, Organic, David, Drew

[Drew]

Awesome. There is a touch more metal removed from the tip, slight, but there. I’ll try fenaggling it a bit.

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Bitcounter

[tcmeyer]

It feels like you’re digging in and applying more pressure when you move thru the belly area because you are.  Even if the pressure you apply is constant, the stone is contacting less area, resulting in more pressure per inch (or square inch).  This can also be the case as you stroke thru the tip area, because there is a sudden drop in the longitudinal length of bevel contacting the stone.  Less area, higher psi.  Higher psi, more steel removal.

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Drew, DaveG, Organic, David, Marc H

[Readheads]

<p style=”text-align: left;”>I suppose then we should ease off on the pressure as we “travel” thru the belly and tip if we want to approach perfect repeatable “symmetry”. I wonder if my accoustic digital pickup would yield useable feedback.</p>

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Bitcounter, Drew

[Drew]

tc, that makes sense. I’ll keep that in mind as a principle of sharpening.

Red, I have no idea what that machine is, or how it works, but if it gives us data, I’d be hungry for it. Is it easy enough to set up and get readings?

This is interesting getting so many different perspectives on this.

[tcmeyer]

I wouldn’t even think about trying to achieve equal PSI as I transition from straight to belly to tip.  You can, however, work at certain sections at a time and use that method to equalize the amount of steel removal along the belly and the tip.  Blending these sections together only takes a few full-length strokes.  More problematic is the fact that a raised ricasso will interfere with your intended uniformity of bevel.  Anytime your stone (or handle) hits the ricasso, the entire face of the stone will take a straight vertical path either up or down – if even for a short segment – cutting a fixed path in the bevel, resulting in an obvious transition seam on the bevel – exactly 3/4″ away from the ricasso.  There are a couple of strategies to counter-act this.  One is to repair the seam manually by working carefully on that specific area.  The other (which I try to follow) is to transition from a diagonal sweep to a circular sweep, trying to touch the ricasso as little as possible.  Again, the object is to avoid straight vertical motions.

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wickededge, Marc H

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