# How to thin a knife?



## madelinez (Sep 6, 2018)

So I've sharpened plenty of knives, and I've "tried" to thin some of those knives behind the edge. But I've never really had any advice on best practice for thinning a knife and was wondering if anyone here could point me to a guide/video/tutorial or just offer their own opinion. I feel like I've achieved basic sharpening skills but still need to learn how to correctly thin or re-profile.

I have stones from 220 grit up to around 8000 grit, as well as an Atoma 140 (attached to handle) for flattening.


----------



## Grunt173 (Sep 6, 2018)

Jon of JKI has many videos on sharpening. Here is one about thinning from youtube.


----------



## madelinez (Sep 6, 2018)

That's a really great video on the theory of thinning, thanks! Maybe I should practice on my old chipped single bevel deba


----------



## Pensacola Tiger (Sep 6, 2018)

When I started thinning, I "painted" the area I was working on so I could more easily see what I was doing. I used a wide marker at first, but then picked up some machinist's layout fluid that is easier to apply.

https://www.amazon.com/dp/B079HHPGMS/?tag=skimlinks_replacement-20


----------



## zizirex (Sep 6, 2018)

Hi, after thinning a knife, how do you remove the scratch that causes by the 220grit stone?


----------



## Pensacola Tiger (Sep 6, 2018)

zizirex said:


> Hi, after thinning a knife, how do you remove the scratch that causes by the 220grit stone?



With higher grit stones, wet/dry sandpaper, "wa" powder, or all three.


----------



## mikaelsan (Sep 6, 2018)

Don't remember how in depth Jon's video is, so this may be repetition. If your thinning a wide bevel knife on the stones, it's just polishing till your happy, holding the knife the same way throughout the process so your scratches match. If your doing a more "mass produced" style knife with rough horizontal? Buffed Scratches, I'm surprised how well 120 grit (euro std) sandpaper blends in and fit the finish. Going the same way as the scratch pattern on the knife helps significantly on the appearance. Then it's just a matter of holding your fingers where you want to remove material, till your happy, I like to keep going till I hit the apex.


----------



## Ilia (Sep 7, 2018)

I wouldn't recommend the use of diamonds...


----------



## Midsummer (Sep 7, 2018)

Ilia said:


> I wouldn't recommend the use of diamonds...



In thining or polishing or both; and why would you not recommend diamonds?

I have seen them used very effectively in polishing. And I have thinned and sharpened with diamonds as well. I would think that it is the size of the abrasive that is its most important characteristic; not its molecular composition. As long as it is harder than the steel itself. But I am always interested in further learning and am far from having it all figured out.


----------



## Ilia (Sep 7, 2018)

Midsummer said:


> In thining or polishing or both; and why would you not recommend diamonds?
> 
> I have seen them used very effectively in polishing. And I have thinned and sharpened with diamonds as well. I would think that it is the size of the abrasive that is its most important characteristic; not its molecular composition. As long as it is harder than the steel itself. But I am always interested in further learning and am far from having it all figured out.


Diamond, unlike natural stones has sharp edges that tear the edge at the micro level...(this can only be seen under a microscope) So I prefer to sharpen the cutting tool on synthetics, and finish on natural stones... Diamonds logical to use when you need to rip off a lot of steel on the knife(but not leaving the edge), then go to synthetic and final prices to produce natural stone...As for polishing the blade, the diamond is absolutely acceptable (but not touching the cutting edge)...


----------



## Ilia (Sep 7, 2018)

therefore, no one sharpens straight razors diamonds...


----------



## Ilia (Sep 7, 2018)

madelinez said:


> So I've sharpened plenty of knives, and I've "tried" to thin some of those knives behind the edge. But I've never really had any advice on best practice for thinning a knife and was wondering if anyone here could point me to a guide/video/tutorial or just offer their own opinion. I feel like I've achieved basic sharpening skills but still need to learn how to correctly thin or re-profile.
> 
> I have stones from 220 grit up to around 8000 grit, as well as an Atoma 140 (attached to handle) for flattening.


stone less than 1000 grit, without the need, I would not recommend to use...


----------



## Pensacola Tiger (Sep 7, 2018)

Midsummer said:


> In thining or polishing or both; and why would you not recommend diamonds?
> 
> I have seen them used very effectively in polishing. And I have thinned and sharpened with diamonds as well. I would think that it is the size of the abrasive that is its most important characteristic; not its molecular composition. As long as it is harder than the steel itself. But I am always interested in further learning and am far from having it all figured out.



Many people believe that a diamond plate like a DMT XXC will make deeper scratches that take longer to work out with higher grits.


----------



## Ilia (Sep 7, 2018)

Pensacola Tiger said:


> Many people believe that a diamond plate like a DMT XXC will make deeper scratches that take longer to work out with higher grits.


It's not blind faith, it's observation through a microscope.


----------



## Pensacola Tiger (Sep 7, 2018)

Ilia said:


> It's not blind faith, it's observation through a microscope.



With measurement?


----------



## HRC_64 (Sep 7, 2018)

another issue with diamonds is they tend to get sheared off ...


----------



## Ilia (Sep 7, 2018)

Pensacola Tiger said:


> With measurement?


Without...But if you don't believe me you can sharpen your razor on diamonds and check on your own face (Although no, don't do that, spare your face )


----------



## Pensacola Tiger (Sep 7, 2018)

Ilia said:


> Without...But if you don't believe me you can sharpen your razor on diamonds and check on your own face (Although no, don't do that, spare your face )



I may give it a try with my DMT 8000 and let you know how it goes.

OTOH, I've found that an Atoma 140 is a very good tool use for thinning, especially if a lot of metal needs to me moved. A King 300 does a fine job of taking out the scratches.


----------



## Ilia (Sep 7, 2018)

Pensacola Tiger said:


> 1)I may give it a try with my DMT 8000 and let you know how it goes.
> 
> 2)OTOH, I've found that an Atoma 140 is a very good tool use for thinning, especially if a lot of metal needs to me moved. A King 300 does a fine job of taking out the scratches.



1) Not recommend
2)Agree, I, too, roughly about this wrote in post #10


----------

