Does this knife need thinning or sandpaper?

Kitchen Knife Forums

Help Support Kitchen Knife Forums:

Delat

Dazed & Confused
KKF Supporting Member
Joined
Dec 31, 2020
Messages
1,284
Reaction score
2,674
Location
Phoenix
I can’t quite figure out if this knife needs thinning or if it’s the finish causing suction that makes it hang up on onions. In the first video you can see it gets stuck doing horizontal cuts on onions, and also sometimes on the vertical cuts. But in the second video it has no problems with a sweet potato.

At the midpoint immediately behind the edge at 1mm it’s .22mm which seems a bit thick. But higher up at 5mm it’s .44mm and at 10mm it’s 1.0mm, which seem reasonable. So the measurements don’t seem excessive except for immediately BTE.

So should I thin a bit, or try some sandpaper first - and if so what grit? It’s a convex grind, so I wouldn’t normally expect suction to be much of an issue.

FYI @Matt Jacobs




 

tostadas

Senior Member
Joined
Jan 27, 2020
Messages
2,496
Reaction score
4,978
Location
California
Based off the dimensions, I'd bet on finish being the issue. I've had knives in the range of 0.25-0.3mm @1mm behind the edge that still did fine through dense stuff. P800 sandpaper is a good spot to test geometry because it's not too grippy (low grit), and not too sticky (high grit).
 

Matt Jacobs

Senior Member
Joined
Feb 13, 2020
Messages
382
Reaction score
570
Location
Washington
That is interesting, it goes through the sweet potato so nicely. I think I had something similar with a Shiro Kamo damascus and it resolved after I ran the blade over a strop for a bit. I have another V-toku2 stainless clad knife that flies through everything but the stainless is polished so that could be part of the difference? It looks like it has to be more than just being too thick.
 

Delat

Dazed & Confused
KKF Supporting Member
Joined
Dec 31, 2020
Messages
1,284
Reaction score
2,674
Location
Phoenix
Based off the dimensions, I'd bet on finish being the issue. I've had knives in the range of 0.25-0.3mm @1mm behind the edge that still did fine through dense stuff. P800 sandpaper is a good spot to test geometry because it's not too grippy (low grit), and not too sticky (high grit).

I have a gap between p400 and p1000 so I’ll give the p1000 a try and see if it makes a difference.

Looks I’ll be making a batch of caramelized onions this weekend 🤣
 

Delat

Dazed & Confused
KKF Supporting Member
Joined
Dec 31, 2020
Messages
1,284
Reaction score
2,674
Location
Phoenix
That is interesting, it goes through the sweet potato so nicely. I think I had something similar with a Shiro Kamo damascus and it resolved after I ran the blade over a strop for a bit. I have another V-toku2 stainless clad knife that flies through everything but the stainless is polished so that could be part of the difference? It looks like it has to be more than just being too thick.

Yup I was sure it was going to wedge on the sweet potato so it immediately had me rethinking the whole thinning project I was planning.
 

McMan

Senior Member
Joined
Feb 15, 2018
Messages
2,513
Reaction score
2,868
I'm actually seeing decent food release (the cut that splits the onion) and the first few cuts on the sweet potato. With slow/deliberate cuts, sticking is more frequently an issue, especially because there is no upswing just downstroke (if that makes sense). Is stiction still an issue when cutting faster?
 

HumbleHomeCook

Whiskey for my men. Beer for my horses.
KKF Supporting Member
Joined
Oct 24, 2020
Messages
3,855
Reaction score
7,580
Location
PNW USA
Based on my own experiences, what I'm seeing absolutely looks finish-driven and I agree with trying to slick it up a bit. I've encountered this multiple times.

Admittedly, I have limited experience compared to so many others but I think I've gotten more performance enhancements from a little edge shoulder relief and finish smoothing than any amount of actual thinning. Not at all saying thinning can't be important of course, just saying the jump forward in performance from the previous can be quite surprising.
 

Delat

Dazed & Confused
KKF Supporting Member
Joined
Dec 31, 2020
Messages
1,284
Reaction score
2,674
Location
Phoenix
I'm actually seeing decent food release (the cut that splits the onion) and the first few cuts on the sweet potato. With slow/deliberate cuts, sticking is more frequently an issue, especially because there is no upswing just downstroke (if that makes sense). Is stiction still an issue when cutting faster?

I tried a fast tip slice (horizontal) through the onion and it got stuck pretty quickly.
 

Delat

Dazed & Confused
KKF Supporting Member
Joined
Dec 31, 2020
Messages
1,284
Reaction score
2,674
Location
Phoenix
Based on my own experiences, what I'm seeing absolutely looks finish-driven and I agree with trying to slick it up a bit. I've encountered this multiple times.

Admittedly, I have limited experience compared to so many others but I think I've gotten more performance enhancements from a little edge shoulder relief and finish smoothing than any amount of actual thinning. Not at all saying thinning can't be important of course, just saying the jump forward in performance from the previous can be quite surprising.

Ok I think I have a plan! A low-angle relief bevel and a rub with p1000 sandpaper.
 

tostadas

Senior Member
Joined
Jan 27, 2020
Messages
2,496
Reaction score
4,978
Location
California
Thanks, good to know. I think my lowest micro mesh grit is 1200, I’ll give it a try first.
1200 micromesh is really scratchy. I don't know how it translates to sandpaper grit, but I think you might end up with a lot of visible scratches with 1200.
 
Joined
Jun 5, 2020
Messages
471
Reaction score
1,215
Location
Presque Isle, Maine
Thanks, good to know. I think my lowest micro mesh grit is 1200, I’ll give it a try first.
5000 grit trizact dry no water or try 0000 steel wool, I do prefer the trizact.

web.jpg
 

Delat

Dazed & Confused
KKF Supporting Member
Joined
Dec 31, 2020
Messages
1,284
Reaction score
2,674
Location
Phoenix
1200 micromesh is really scratchy. I don't know how it translates to sandpaper grit, but I think you might end up with a lot of visible scratches with 1200.

Ooooh, thanks for pointing that out! I just assumed it was the same grit scale as sandpaper.

 

Delat

Dazed & Confused
KKF Supporting Member
Joined
Dec 31, 2020
Messages
1,284
Reaction score
2,674
Location
Phoenix
Success! Thanks for the tips guys. I thinned immediately behind the edge, basically adding a 5 degree relief bevel. That took it down from .2mm to .1mm @1mm BTE.

As @tostadas warned, the lower micro mesh grits were indeed scratchy. I started at 2800 and worked my way up to 4000. The original finish was probably sandblasted as the sanding revealed all the belt sander marks. The blade now performs much better - not quite Myojin smooth so I think I’ll thin it more a bit higher up (it measures 1mm @10mm BTE, my Yoshi and Myojin are around .8mm) which will help me take out some of those sanding marks anyway.

It’s still a bit reluctant on the horizontal cuts, not quite sure if it’s thickness or stiction at this point but I’ll continue experimenting with both.

I should mention that the maker, Brian Hanson, is a former chef and this is his budget line of knives intended for professional use by line chefs. So the original thicker geometry is appropriate for that application. At $250 and with the 20 mins of tuning work I put in, I think it’s a terrific value for a Western maker especially for a pro cook.




Here’s the original OOTB finish.
D7305DAB-8068-42F8-BEDB-BA7FE60EDB0A.jpeg


Post-tuning, you can see my thinning for the first few mm BTE, and the post-sanding finish.
CC2CD523-9BAD-4C60-8741-2FD0F8DD3439.jpeg
 
Top