Diving into Thinning

[Dave]

Hello friends,

I have acquired one or uh... seven knives that could use a little extra love and am willing to totally **** one up for science and learning, but I don't know where to start. I know the very basic premise behind thinning and have watched a few videos on the "how to", but need some advise on a good stone, and perhaps anything else I might be unaware of.

My current set-up is an Atoma 140, SG500, SG2000; and I'd really like to stick to splash-and-go stones if possible. My first thought was to go for an SG220, but not entirely sure that's the optimal route.

Any advice would be appreciated!

 

[Just a DK]

Hello friends,

I have acquired one or uh... seven knives that could use a little extra love and am willing to totally **** one up for science and learning, but I don't know where to start. I know the very basic premise behind thinning and have watched a few videos on the "how to", but need some advise on a good stone, and perhaps anything else I might be unaware of.

My current set-up is an Atoma 140, SG500, SG2000; and I'd really like to stick to splash-and-go stones if possible. My first thought was to go for an SG220, but not entirely sure that's the optimal route.

Any advice would be appreciated!

Pick a sacrifice.

F*** its s*** up. Repeat until knife is ruined.

Second one might be better…

By 3rd knife you should have at least a sense of what each stone does.

Oh… flatten and clean surface often. Rest when tired or messing up too much and come back to it…

 

[Dave]

Pick a sacrifice.

F*** its s*** up. Repeat until knife is ruined.

Second one might be better…

By 3rd knife you should have at least a sense of what each stone does.

Oh… flatten and clean surface often. Rest when tired or messing up too much and come back to it…

Ok if I'm gonna need to kill two of them I'll probably start with one of my old beaters before trying to thin the Maillet Nakiri I actually want to thin lol

SG220 seem like a good choice to start?

 

[Just a DK]

Oof.. there are definitely people who do this a lot more. I think the SG220 is ok in a pinch, but I do not prefer it to thin.

But are you thinning the bevel to getting thinner bte due to oversharpening (I think most simon's are stone ready / zero ground so shouldn't need a lot of work)? or like looking to move the shinogi up to create a more acute angle to cut with.

 

[Dave]

The latter. Want to lessen some of the wedging.

 

[Just a DK]

In that case don't listen to an novice like me that can barely get a bevel thinned acceptably.

I'd think for that kind of heavy duty work most people here would recommend you get a diamond stone.

 

[M1k3]

https://www.homedepot.com/b/Tools-Power-Tools-Grinders-Angle-Grinders/N-5yc1vZc2fw

 

[Dan-]

3M wet or dry on a Kasfly is really the best if you aren’t using diamonds or power tools

Helps to have your favorite beverage(s) to pass the time too.

 

[HumbleHomeCook]

Member @noj has a good thread on thinning. Worth finding it.

Thinning can be challenging but in general isn't terribly difficult. Take your time, look at what you're doing and how it is going. Follow the original grind unless you intentionally want to change the base geometry which I wouldn't wade into starting out. You can always remove, you can't put back on.

Thinning and looking good when you're done is the real challenge.

 

[aporigine]

…
Thinning and looking good when you're done is the real challenge.

tell that to Jenny Craig!

 

[JPAU]

3M wet or dry on a Kasfly is really the best if you aren’t using diamonds or power tools

Helps to have your favorite beverage(s) to pass the time too.

Audiobooks would work!

 

[JPAU]

Member @noj has a good thread on thinning. Worth finding it.

Thinning can be challenging but in general isn't terribly difficult. Take your time, look at what you're doing and how it is going. Follow the original grind unless you intentionally want to change the base geometry which I wouldn't wade into starting out. You can always remove, you can't put back on.

Thinning and looking good when you're done is the real challenge.

‘Treat it like seasoning a stew’

 

[Justinv]

SG220 is a fine starting stone for general thinning, then SG500 and whatever comes next.

 

[Martyfish]

This is a basic thinning guide that I made years ago. I'd like to think that I have improved a bit since then, but the guide is still relevant. There is also a lot of information in the captions.



I use a JNS 300 for thinning and have been very impressed with it, however I usually thin soft clad knives. If you're thinning hard, wear resistant monosteel then I'm not sure it'd be the right tool for the job.

Thinning itself is relatively easy, because you can see pretty clearly what is going on, due to the deep, ugly scratches, and material removal is so slow that it's hard to do any major damage. One piece of advice is to pay special attention to what you are doing once you reach a zero grind (no edge bevel), because from this point you will alter the profile and you'd normally want to do that evenly along the blade. I try to avoid reaching a zero grind on coarse stones and leave that for medium or fine stones to avoid losing height and accidentally messing with the profile.

Another thing worth nothing is that the best way to view and compare convexity is by using a credit card or similar flat surface as shown in the video below:



Scratch reduction and refinishing are the most time consuming processes. Patience and ensuring all deep scratches are removed before proceeding is the key here, regardless of the abrasive (whetstones, sandpaper, loose abrasives, abrasive pastes, etc.).

Some of my more recent DIY efforts can be found in the thread below and I usually try to include useful information along with pictures in the event that you are interested:

https://www.kitchenknifeforums.com/...thinning-refinishing-and-handle-making.68639/

 

[Dave]

Thank you all for the input, especially @Martyfish for your extensive post and link to even more info. Going to do some more reading before moving forward.

Thanks again!

 

[Matus]

Are these knives stainless or cabon steel, monosteel or sanmai?

 

[Dave]

Are these knives stainless or cabon steel, monosteel or sanmai?

The first two I want to tackle are san-mai 135cr3 with wrought cladding.

 

[Matus]

The first two I want to tackle are san-mai 135cr3 with wrought cladding.

That sounds expensive to learn on

I would say - get a Bester 220 (similar to SG220, but you get a lot more stone for your money). Try to avoid using the Atoma 140 unless the knives are in super bad shape. I would start from far away from the edge and work myself towards the edge as I am thinning, as otherwise you have a much bigger risk to over-grind the edge.

A very useful help will be a (wide) permanent marker to check where you are removing steel and whether you are grinding in lowspots (yes, you can produce a low-spot on a perfectly flat stone). Also if available - get a digital calipers, measure the blade along the edge at different distances and put those on a paper. Consider how much material you want to remove where - and keep measuring as you work on the knife.

 

[mockit]

If they really need thinning I’d consider reaching out to the smith or someone who can polish and is willing to do some light maintenance for you. If you want to learn thinning and polishing I’d 100% get a knife from Knife Japan or off BST and learn how to set a bevel. Take it from someone who has learned this the hard way…

 

[kdizzog6]

Id say go for it. I experimented with a Shinko Seilan for my first project and it came out fantastic. I believe its all about how many high / low spots you have to thin and how well the original grind was made and what type of grind you are working with. But if you have a stone that is aggressive enough and a good finisher, and a couple in between it is very satisfying. Of course, time, patience, and having a day or two of carpal tunnel. My seilan will out cut a knife 10xs the cost, I took it down to a zero edge and then put a micro bevel on it. It is now an amazing cutter that I often loan out to others who want to experience cutting bliss without a huge price tag.

 

[Matt Jacobs]

I am not good at this by any means but I have had pretty good luck with making knives perform better. I like Murray Carter's advise of, you dont have to make it perfect just make it better. I do a little bit at a time on a good knife. I typically start by just relieving the shoulders than using it and seeing what I want to thin next. Once I feel its cutting better, I try and work on the finish. As long as it is better than when I started I just use it for a bit and go at it again in a few weeks with my new plan. That way I never ruin a knife, just improve it. Now if its a beater, I love the idea of removing the handle and going to town like @Martyfish Again, I agree with others on sandpaper, not just for thinning but refinishing as well. I am in awe of people who can polish with stones, I dont have the patience but I can make it look good with sand paper. I also have a cheap 1x30 with a scotchbrite belt. It does wonders on monosteel knives that were originally finished that way. I have taken a few scratched up Muteki's back to that and made them look new in seconds.

 

[Delat]

For thinning jobs more serious than a relief bevel, I like to take a measurable, objective approach. Measure several of your knives at multiple points to establish a baseline of what you like so you have a target to shoot for. Take additional measurements as you thin so you know where to adjust and focus your efforts. For me personally, I’ve found that the 5mm and 10mm areas are critical in establishing the cutting feel I like.

Below is a screenshot of a spreadsheet I keep for measurements. Where I have a knife listed as a 1.1 or .1, .2 is post-thinning. My measurements aren’t individually particularly precise or accurate, but they do group around the way the knives feel when in use. I use both an SG220 and Nanohone DR100 for initial thinning.

 

[noj]

Member @noj has a good thread on thinning. Worth finding it.

Thinning can be challenging but in general isn't terribly difficult. Take your time, look at what you're doing and how it is going. Follow the original grind unless you intentionally want to change the base geometry which I wouldn't wade into starting out. You can always remove, you can't put back on.

Thinning and looking good when you're done is the real challenge.

https://www.kitchenknifeforums.com/threads/thinning-questions-yet-another-thread.62237/
https://www.kitchenknifeforums.com/threads/next-steps-on-project-knife.71342/

 

[noj]

That sounds expensive to learn on

I would say - get a Bester 220 (similar to SG220, but you get a lot more stone for your money). Try to avoid using the Atoma 140 unless the knives are in super bad shape. I would start from far away from the edge and work myself towards the edge as I am thinning, as otherwise you have a much bigger risk to over-grind the edge.

A very useful help will be a (wide) permanent marker to check where you are removing steel and whether you are grinding in lowspots (yes, you can produce a low-spot on a perfectly flat stone). Also if available - get a digital calipers, measure the blade along the edge at different distances and put those on a paper. Consider how much material you want to remove where - and keep measuring as you work on the knife.

Excuse intruding in someone else's thread. If appropriate, feel free to PM.

When you mentioned producing a low spot on a flat stone, were you thinking of grinding a flat area within a convex surface, or something else as well? I ask because I sometimes get an impression that when thinning or polishing san mai, that abrasive gets stuck just above the hagane and creates a low area. It could just be my imagination, or remnant of some concavity in the original grind.

 

[Dave]

Thank you all for your very informative responses. I have not had time to give all of them a thorough read, but so far I've gathered...

1. Do this on a beater knife first, because chances are you'll still **** it up the second time.
2. The SG220 is not the ideal stone for this, but is worth considering. Also sandpaper is probably better.
3. Set a target width and constantly measure progress.
4. Most importantly, stop by the dispensary or liquor store before starting the process.

 

[Cliff]

I will echo: don't use the Atoma for thinning. Save it for the stones. I like the Debado 180, but I gather they are variable. I find a 320 slow going and prefer something coarser.

 

[Blumbo]

I feel like my debado 180 both dishes and kicks up too much mud yet also somehow glazes before I make significant progress honestly it turned me off stone finishing for some time because of how messy and unrewarding it felt relative to sandpaper

 

[aporigine]

Excuse intruding in someone else's thread. If appropriate, feel free to PM.

When you mentioned producing a low spot on a flat stone, were you thinking of grinding a flat area within a convex surface, or something else as well? I ask because I sometimes get an impression that when thinning or polishing san mai, that abrasive gets stuck just above the hagane and creates a low area. It could just be my imagination, or remnant of some concavity in the original grind.

I’ll take a swing at this.

Steel flexes under finger pressure. So if you take a nice flat bevel to a flat stone but only apply pressure in one spot, you can excavate the bevel at that spot, forming a low area.

When it happened to me, it was astonishing, then angering … finally instructive. Now I try to keep my fingers moving behind the edge so as not to literally get into a rut.

 

[noj]

I’ll take a swing at this.

Steel flexes under finger pressure. So if you take a nice flat bevel to a flat stone but only apply pressure in one spot, you can excavate the bevel at that spot, forming a low area.

When it happened to me, it was astonishing, then angering … finally instructive. Now I try to keep my fingers moving behind the edge so as not to literally get into a rut.

Interesting idea, I will watch for that. I tend to see it in a long band just above the hagane, which is harder, but perhaps not impossible to understand with your idea.

 

[aporigine]

Interesting idea, I will watch for that. I tend to see it in a long band just above the hagane, which is harder, but perhaps not impossible to understand with your idea.

Yeah not sure my explanation holds. Maybe move fingers toward and from edge …