Thinning

Hi all,

Another area that pops up frequently on the path to sharpening enlightenment is the subject of Thinning.

So I am working on a video of how I do this but before that, I want to get some feedback from some other sharpeners to see if they can add anything and also to confirm that my approach is sound.

Here is what I am working on so far.

Thinning: 

For me there are three types and they all have something in common, i.e[u]. a Sharpening Angle and a Thinning Angle. [/u] Also, the Thinning Angle (TA) is not a fixed angle, it depends on the thickness of the knife and just how much I want to remove.

AGGRESSIVE THINNING:

     This is the way I handle a knife that is really thick, yesterday I had a Global that was terrible, it could be razor sharp but so thick it would be unpleasant to use. 

I lie the knife flat on the stone, so I am thinning at zero degrees and going at it with a lot of pressure and a 220 grit stone. I continue until this Relief area is highly polished, I am not touching the edge of the knife, there is no burr formation. 

After I am satisfied with the geometry behind the edge, I then raise the angle by 3-4 degrees, to whatever the knife should be sharpened at and then sharpen it as I normally would, at the SA.

Pros: I  find that this method can have a dramatic effect on the performance of the knife and sharpening it is very easy. The Relief area, the area that was thinned can have a very beautiful level of polish. 

Cons: Can easily scratch the blade, in fact the blade will be scratched. (It can be taped but the tape can wear off as well). This also can be very time consuming. 

(This is done after what could be years of sharpening with no thinning done at all prior to this point)

MODERATE THINNING:

This is basically the same thing however I am not thinning at zero degrees, the TA is slightly more acute (3-4 deg) than the SA (Sharpening Angle)

Pros- Also very effective at improving the performance of the knife.

Cons: I am not aware of any, that doesn't meant there is none, I just have figured that out yet.

(Thinning may have been done or the knife is not that old, it isn't too bad yet)

PASSIVE THINNING:

This is where I thin the knife within a few sharpening sessions, the knife isn't thick but it is means of trying to maintain the level of thinness currently seen on the knife. It is something I would do often and would not take long. The TA would again be a 3-4 deg more acute that the SA>

PROs: I think that if you catch the knife soon enough it may be the easiest and best way to maintain the performance of the knife assuming it was thin enough to perform well in the first place. 

CONs: I can't think of any.

Now....there are people who choose a thinning angle and continue to grind until the edge of the of knife is reached and they form a burr. They are creating a new sharpening angle and a wider bevel. 

I don't call this thinning, it is modifying the knife, it can have benefits but I wonder if this also has a negative impact on edge retention. 

This is a work in progress for me, I won't shoot the video until I am completely comfortable and have heard back from those smarter than I am.

Peter