New kurokumo with uneven-wavy edge

[dsk]

I recieved a 210mm kurokumo recently from kns and noticed there was a bit of wobble near the heel. When I bring the edge down onto a surface I can feel a slight pivot-bump, rather than a smooth action from tip to heel. I cant visually percieve of any overgrinding, and the blade seems straight.

None of my current or past knives have had this issue ootb. Was it just sloppiness when they gave it an edge, or is it potentially a structural hassle down the line?

 

[HRC_64]

The types of overgrind that are problematic don't show up as outward-wobbles in the profile but rather as hollows (ie, they are low spots between two bumps, not one). So if you have a single problem its probably not an issue, but if you have a series of problems you need to look more closely. This is typically discussed under keyword: overgrind.

 

[Corradobrit1]

Really only a problem if there's a 'hole' in board contact resulting in incomplete cuts.

 

[refcast]

A couple things could be going on (a picture would be really helpful):

(1) There is an overgrind during manufacturing that lead to a recurve in the blade profile. This can be fixed by sharpening the profile to the desired shape.
(2) The profile has an abrupt flat spot, by maker design or otherwise. Also fixed by sharpening.
(3) The knife truly has a "wavy-edge". That is, if you look down the edge, from heel to tip, with the edge up: the edge wiggles like a wave instead of following a straight line. This can eventually be remedied by sharpening, though professional help might be nice. This would be a structural hassle.

The profile is the edge when you look from the side of the knife.
The wavy edge itself is if you look at the edge with it facing at you.

Based on your details (and lack of certain ones), I think it is (2).

 

[dsk]

A couple things could be going on (a picture would be really helpful):

(1) There is an overgrind during manufacturing that lead to a recurve in the blade profile. This can be fixed by sharpening the profile to the desired shape.
(2) The profile has an abrupt flat spot, by maker design or otherwise. Also fixed by sharpening.
(3) The knife truly has a "wavy-edge". That is, if you look down the edge, from heel to tip, with the edge up: the edge wiggles like a wave instead of following a straight line. This can eventually be remedied by sharpening, though professional help might be nice. This would be a structural hassle.

The profile is the edge when you look from the side of the knife.
The wavy edge itself is if you look at the edge with it facing at you.

Based on your details (and lack of certain ones), I think it is (2).

Good insight, id say its closest to 2. Close to where the curve meets the flatspot there was a wave, then about 3cm from the heel it laid flush to the board. I've taken the knife to a 600 plate and smoothed it out, theres still a barely present hint of the wave, but its functional now without any accordion effect on chop cute. Just based on this fix, it shouldn't be a big deal and within the year it should be perfectly smooth and the edge is not warped by my eye.

I would have had to bust out my dslr and macro lens to capture the wave, as I couldn't do it on a smartphone.

 

[Michi]

I would have had to bust out my dslr and macro lens to capture the wave, as I couldn't do it on a smartphone.

Easy way to check: put the blade down on a perfectly flat surface (double-check with a straight edge). Put a light source behind the knife and look at the edge from the other side almost level with the surface the knife rests on. If any light makes it through between the edge and the surface, you still have a recurve there.

 

[dsk]

Easy way to check: put the blade down on a perfectly flat surface (double-check with a straight edge). Put a light source behind the knife and look at the edge from the other side almost level with the surface the knife rests on. If any light makes it through between the edge and the surface, you still have a recurve there.

Yeah it's one of the first things I do with any knife, slide the edge along some flat wood and peek for any apparent gaps, the kamo was the first to actually have some. I was more referring to photo documentation of the issue with clarity.

 

[Ivan Hersh]

I would contact the seller and get an exchange.