Dihedral Angles in Knife Sharpening

[Anonymous]

That’s great info.

So when you have done that and clamped it for best angle consistency, if you attach your angle cube and check the angle variance at several points from the heel, to the straight, to the curve, to the tip.  How much angle variance is there typically if you get it aligned as good as possible?

[Marc H]

The knife’s clamping position and the bevel angles are two separate things, though they are related.

This method, I described above, is to determine the “best” or most efficient clamping position to use when sharpening a knife.  This is called the “sweet spot”.  The sweet spot in turn allows us to find or determine the existing bevel angles in order to sharpen the knife well, while maintaining the existing bevel angles.  When the knife is clamped in it’s “sweet spot” the sharpening stones should contact the knife edge well, down the entire length of the knife.  This is strictly about efficient knife placement for clamping.

You can narrow down or fine tune the “sweet spot” clamping position when combined with the sharpie method.  By applying a sharpie then observing where the sharpie ink is removed from the knife bevels using fine grit stones, you can re-position the knife shifting it ever so slightly so where the stones contact the bevels are consistent positions along the bevels, and across the entire length of the knife.

The determination of the bevel angles is another, more specific, process.  This is done after the “sweet spot” clamping position is first determined.

With the knife clamped in the vise jaws in it’s “sweet spot” position, using the sharpie method we can observe and match when the sharpie’s ink is being removed.  While repeatedly applying and reapplying the sharpie ink, while making angle and micro-angle adjustments we find when the ink is best removed from the entire bevel while running a fine grit sharpening stone with very lightly applied pressure, across the bevels.  We are simply trying to remove the ink, not any steel.  It is a give and take situation.  We’re simply looking for the angle setting(s) that coincides with when the ink was removed most completely from the entire knife edge.

When this best postion is found then measured with your properly zeroed angle cube it broadly indicates the existing bevel angles of that clamped knife’s edge.  Depending on how well the knife was made, or how well the knife was last sharpened will be shown by how well you can adjust the guide rod angles so the stones match along the entire knife length.  Seldom do we find that the bevel angles are consistent from knife side to side or even down the length on just one knife side.  That is unless the knife was last sharpened well using a Wicked Edge Sharpener or it was precision machine sharpened from the knife’s maker.

We are trying to find the angle setting that allows for the most efficient removal of the sharpie ink, on average.  With that observed and measured angle we can then choose an angle setting that will allow us to best sharpen the knife to the angle of our choice that is best for our needs and applications.

Even if you decide to re-profile the knife to a different angle,  one of your choosing from the outset, you should still determine the “sweet spot” first, in order to sharpen the knife well and efficiently with the least amount of steel lost or wasted.

Marc
(MarcH's Rack-Its)

• This reply was modified 3 years, 9 months ago by Marc H.

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[Richard]

I think you talk about this in you ‘Finding the Sweet Spot’ thread, right? It works, that’s for sure.

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Marc H

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