Wicked Edge and edge geometry

TRfromMT

TRfromMT

Joined
Jan 4, 2016
Messages
5,666
My question is about how the geometry/angle will change from heel to tip because the tip is lower in elevation. If you follow the W.E. directions the tip will have a more obtuse bevel as a result.

When I set up a blade in my W.E., I imagine a straight line between the point and the very heel of the edge and I set that imaginary line parallel to the base. This "averages out" the geometry along the length. I set the actual angle at the crown, centered over the clamp.

Incidentally I also find this approach aids in adequately clamping full flat grinds, such as the PM2 blade. Dropping the handle and raising the tip allows the clamp to work better, clamping on the full width of the jaws, as well as evening out the bevel along the length.

Anyone else do this? I've never seen this technique recommended or discussed. All W.E. videos and knowledge base articles have the spine horizontal to the base.

Curious if I'm the only one who drops the handle in their setup.
 
TRfromMT said:
My question is about how the geometry/angle will change from heel to tip because the tip is lower in elevation. If you follow the W.E. directions the tip will have a more obtuse bevel as a result.

When I set up a blade in my W.E., I imagine a straight line between the point and the very heel of the edge and I set that imaginary line parallel to the base. This "averages out" the geometry along the length. I set the actual angle at the crown, centered over the clamp.

Incidentally I also find this approach aids in adequately clamping full flat grinds, such as the PM2 blade. Dropping the handle and raising the tip allows the clamp to work better, clamping on the full width of the jaws, as well as evening out the bevel along the length.

Anyone else do this? I've never seen this technique recommended or discussed. All W.E. videos and knowledge base articles have the spine horizontal to the base.

Curious if I'm the only one who drops the handle in their setup.
Click to expand...

Your reason really isn't accurate.

The blade is set in the clamp based on the relation of the belly/tip area... as shown HERE. (Note the angles on the diagram on the page). So you can have a "more obtuse", "less obtuse", or set it so it's the same angle along the entire blade. It has been shown HERE (and other places), that the angle doesn't change along the straight portion... so set the blade based on the belly/tip area.

The "straight line between the point and the very heel of the edge"... works by coincidence. It was tried and "debunked" in the W.E. forum a few years ago (can't find the thread right now). It will work on some blades, but there's no actual reason for it... (even though lots do it... you'll notice that it's usually on similar length/shape blades).

You can tip the blade up or down, to help accommodate various blades. (That's why W.E. has the "Advanced Alignment Guide"). Again the belly/tip area is how you set the blade. BTW... the pivot/rods the stones ride on can't "see parallel"... it has no idea if the blade is parallel to the clamp or not. It's been discussed in the W.E. forum (the AAG was the result of that).

So, nothing wrong with what you're doing... just the reason behind it. ;)
 
On a continuously curved blade (i.e. the PM2), with the blade set spine-parallel to the base, the geometry will absolutely change at the tip. I do understand the geometry along a straight edge will not change if it is set parallel to the base. The geometry is not established by the length of the edge so much as it is set by the elevation relative to the base. The elevation along a parallel line is constant, therefor constant geometry.

I am speaking of averaging out for a non-constant/non-straight edge.
 
Last edited:
On re reading this, I see cbwx34 cbwx34 's point about my reasoning.

It would have helped to clarify I was talking about blades without any appreciable straight edge, and about FFG and tapered blades.
 
The key is being consistent in your clamping, so that every following sharpening session maintains whatever edge geometry that you like.

Personally, I like to have the section of the edge from the belly up to the tip sharpened at a more aggressive angle to improve penetration and detail work.
 
TRfromMT said:
On a continuously curved blade (i.e. the PM2), with the blade set spine-parallel to the base, the geometry will absolutely change at the tip. I do understand the geometry along a straight edge will not change if it is set parallel to the base. The geometry is not established by the length of the edge so much as it is set by the elevation relative to the base. The elevation along a parallel line is constant, therefor constant geometry.

I am speaking of averaging out for a non-constant/non-straight edge.
Click to expand...

If the whole blade is curved from heel to tip... then technically the only way to get a consistent angle, would be to match the radius of the rod the stone is attached to. BUT, the difference is so slight it doesn't usually matter, although some have actually modified their setups to accommodate this, (by changing the height of the clamp relative to the angle rod).

Again, it also doesn't matter that the straight edge be set parallel to the base. The pivot the the rod is on has no idea what "parallel" is... it travels in a circle. Here's a post and picture in the W.E. forum that talks about this... and the whole thread talks about the concepts behind the AAG. Advanced Alignment Guide thread.
 
cbwx34 said:
If the whole blade is curved from heel to tip... then technically the only way to get a consistent angle, would be to match the radius of the rod the stone is attached to. BUT, the difference is so slight it doesn't usually matter, although some have actually modified their setups to accommodate this, (by changing the height of the clamp relative to the angle rod).

Again, it also doesn't matter that the straight edge be set parallel to the base. The pivot the the rod is on has no idea what "parallel" is... it travels in a circle. Here's a post and picture in the W.E. forum that talks about this... and the whole thread talks about the concepts behind the AAG. Advanced Alignment Guide thread.
Click to expand...

Good stuff cbwx34 cbwx34 . I'm going to have to go study this. I thought I had the spatial geometry of the slider arms all worked out in my mind. Now I need to think about it some more.
 
I've found a good way to get an idea of what's going on with the angles at various points on the blade is to just use an angle cube and experiment with it a little bit. Even those angle finder apps for your phone are pretty accurate.
 
TRfromMT said:
Good stuff cbwx34 cbwx34 . I'm going to have to go study this. I thought I had the spatial geometry of the slider arms all worked out in my mind. Now I need to think about it some more.
Click to expand...

It took me a long while to figure this out... 'cause it seems counter to what I thought it should be. (And it still makes my head hurt...). :confused:

Bill3152 said:
What's the angle difference in all this? I would assume there always is one anyway.
Click to expand...

I actually don't think that is answerable (at least not without setting some parameters...). :eek:
 
You must log in or register to reply here.
Back
Top