Thinning - The Buzzword

Hi all,

     One of the sharpening hot topics that pops up all the time is Thinning.  I'll give you my thoughts on this:


     As  you know, the process of thinning results in reducing the width of the knife from a cross sectional perspective behind the edge, reducing the width of the "shoulders" of the blade. This is done to restore geometry or just improve performance.

     To me, thinning is a buzzword that too many people are using to recommend the process be done on a knife. It seems to me that if there is problem with the way the knife is working, it just needs thinning. I'm talking in most cases about knives that are already thin and are less than two years old, often less than a year old. Owners browse forums and see the word thinning as the answer to a problem, or, worse yet, something that is required.

   

     A knife does not become thick if its just a year or two old and if it hasn't been sharpened so why thin it?

    Yes, thick knives that are made thick at the factory or become thick with use and repeated sharpening will definitely benefit from a thinning.

   However, if the knife is not slicing as well as the owner thinks it should be, perhaps the problem is not that it needs thinning but it needs to be sharpened properly. That would be the first thing I think about. I am just suggesting that thinning may not be the answer being looked for, it may be sharpening instead.

     Thinning is not easy and it can impact the way the knife looks. I have nothing against thinning, I do it a lot but not every single knife needs to be thinned. Be careful what you read and who the author is. 

Clearly if the knife is damaged, thinning is common follow up after the repairs are made because the new edge is often higher up in the thicker part of the blade.

     

I taught a member of the Royal Canadian Mounted Police to sharpen his knives the other day and he gave me this beautiful coin.

     Here is a knife that was severely damaged. I did have to thin this one a little after I repaired it. I say a little because the knife was ridiculously thin to begin with.

     Again, I love thinning a knife,  my point is that I love thinning knives that need it. It is usually not my first option when I get a knife. I inspect it for thickness and then go from there. If the owner has pointed out a problem with slicing performance, I think about sharpening it first.

I appreciate you visiting my little Blog..

Peter Nowlan

Pressure - Making it simple

Pressure Finger Placement

Happy New Years folks and thank you for coming back.

    As you may know, I used several levels of pressure when I sharpen a knife, four to be exact. However, what if people find that difficult to follow, what if I were to use two levels of pressure instead?

   First of all, I want to make it clear why I use different levels of pressure in the first place, it may not be obvious to all:

     When I pick up a knife, I do the same thing every time, a couple of thousand times a year at least. I look at the edge to make sure that it is ready to be sharpened, I check to make sure that there is no damage to rectify, no broken tip, no chipped edge, nothing that will hinder the sharpening process. If you only sharpen your own knives it is still a good habit to follow. In other words, I don't pick up the knife and start grinding metal away until a burr is formed before an inspection.

    This inspections enables me to determine my starting points, what stone I will begin with, what angle to sharpen at and what my finishing stone will be. I'll break that down:

1. First stone will always be a coarse stone, 120, 220, 320, 400, 500, 600 or 800 grit. (I'm sharpening the knife not honing it, otherwise I would be looking at a medium grit stone)

2. Angle is easy, for soft knives, 15-20 degrees per side, for hard knives, 10-15 deg per side.

3. Finishing grit, the final stone that I use will be either 1,000, 1, 500 or 2, 000 for soft knives and either 5,000, 6,000 or 8,000-9,000 for hard knives.

I can simplify the angle issue even further, I can use my pinky as a guide for just about every knife except for the finest Japanese knives where I will drop to 11 or 12 deg per side.

  Back to pressure.

Let's use two levels of pressure only instead of four, it works well.

(Some folks use one level of pressure throughout, I don't, I never will so I won't be discussing it here)

Pressure Level 1 - BURR FORMING PRESSURE

     I pick up the knife and see how dull it is, I then pick up my 500 grit Shapton Glass coarse stone (as an example). Of course, if you only have one stone, that is the one to use:)

     I use whatever pressure is necessary to form a Burr, so at this stage it is me and the stone working together to get that critical stage of the process underway. If my pressure is to light, I won't get the burr formed, it is a waste of effort,  so some pressure has to be applied. I always start moderately, using less pressure than I think I need just to see how it goes, how the steel in the knife reacts. Some steel is very resistant to abrasives and is difficult to sharpen. Other steel is very easy, like hand made Japanese knives, white or blue steel is fantastic to sharpen.

    My fingers are placed near the edge as in the first picture above. These are my pressure fingers, I use two fingers and the sharpening is taking place below the fingers. I am very careful here to use the entire surface of the stone to promote even wear, to keep the stone flat as long as I can before I need to flatten it. 

   This is the most important part of the process, proper burr formation and it can only be done with at least a little pressure. (Sharpening certain knives like a Takeda is different if using a hand held Takeda Whetstone).

   I work on this stone using this level of pressure, moderate to heavy, until I have formed a burr on both sides of the knife, consistent in size and from tip to heel. 

THIS IS THE ONLY time I will use this level of pressure on the same knife.

Pressure Level 2 - BURR REMOVAL PRESSURE

     This is a fifty percent decrease in my starting pressure, BUT, I am on the same coarse stone. (I used to switch to a medium grit stone but I stopped doing that in 2012) I now use the same coarse stone but decrease pressure significantly. My goal here is start the burr removal process, the cleaning of the edge. 

I move from tip to heel, heel to tip, flip the knife, of switch hands, then repeat on the other side.

I now conduct the LIGHT TEST and if I pass, I move to the next stone. 

    Assuming I have moved to a 1,000 grit stone for example, I finish the knife off using light pressure, enough to refine the edge, it's nice and light as I don't want to form any more burrs, I want to reduce the depth of the scratches created in the bevels by the first stone and I do this by using the more gentle abrasive powers of the medium stone. I could easily move to a 2,000 grit stone here because I have made sure that the knife is sharp, as sharp as I can get it on the coarse stone.

   So there you have it, the knife finished using only two levels of pressure. I use a leather strop next or before that, I may use a finishing stone like a Suehiro Rika 5,000 and very very light pressure before the strop. All in an effort to clean the edge.

Thank you for visiting, or coming back.

Respectfully

Peter Nowlan