Sharpening and Knife Life


Well-Known Member
I have been doing some sharpening lately on a specific knife and measuring the loss of steel as I go. I started off sharpening the knife 10 times each session, with destressing the edge by cutting lightly into the stone 4 times and then making 50 passes per side on my 1000 grit King water stone. I repeated this 10 times in one evening and found it removed about 0.01" from the width. The next time I dropped the number of passes down to 30 per side, with everything else the same. Surprisingly, the width removal went to about 0.005". Next, I tried a different stone, otherwise the same, 10 times, 4 destressing passes, same angle (17 dps). The two differences were this was a Norton Economy stone and I went free hand. The other sessions were done on my angle block. This removed about 0.009"

Now, I intend to do this 30 times, to simulate nearly a year of daily, metal removal sharpening. So far, each individual sharpening seems to be removing 0.001" or less, and with care, it's about half that. A small burr is formed each sharpening, so I know I'm reaching the apex and beyond. Ideally, I'd like to be able to not form a burr, but just barely apex the edge, though a small burr will always be there at this stage, even if just on some sections of the edge.

I feel most people don't sharpen their knives nearly on a daily basis, so this might well represent 10 years of sharpening by the time I'm done.
Ok, round 4 is done, up to 40 full sharpenings. This time the blade lost 0.008" of width. I changed stones again, going to my Norton 220 waterstone. This is clearly the way to go if efficiency is the goal. I was able to apex the edge (remove the shiny flat from destressing) and go beyond to get a little burr to form in just 10 passes per side at 17 degrees per side. I also tried to measure the changed in just one sharpening, from destressed edge, to sharpened/apexed, to destressed again, I could not see a difference with my calipers, but they're only graduated to the nearest 0.01". Still, it was dead on the 1.280" mark before and after.
This is one of those things that comes up often and is based in reality but is a little distorted.

A lot of people get frustrated with sharpening and resort to using high powered sharpening equipment, pull through grinders or high speed wheels or even angle grinders. Take a knife and press hard and pull it through one of those motorized sharpeners 40 times and see what is left.

Here is the question I would ask - why does sharpening have to remove any material at all from the width of a blade, only blunting should do that. If this isn't immediately obvious then just take a simple piece of wood and try to make a point on it without shortening the wood, it is clearly possible with a little care if you just mark two lines and cut to them. Now look at the size of the point you are making compared to the size of the point you make on a knife.

This is one of the reasons unfortunately that people have a kind of fear about sharpening thinking it can ruin / wear out a knife too fast and try to avoid it like a plague. In reality, the only way you lose steel in sharpening is if you form an apex and then keep grinding until you form a significant burr and just repeat that over and over.

Unfortunately that is also a common method of sharpening.
Was free hand sharpening used or a controlled angle used? I would think there would be a difference in the amount of material removed between the two techniques.

It was done using an angle guide. I have a video on my youtbe channel sharpening on my sharpening guide blocks. I used a 17 degree per side block.