Home

What happens to an edge while sharpening?

What happens to an edge while sharpening?

by Ola Pettersson | Nov 22, 2024

OK, this doesn’t look like much to any kind of knife or honing expert, but it’s the reality when using 150 micron (0.15 mm) large diamonds in a filing motion to quickly remove material with the purpose of getting the sides to meet at a nice sharp edge. In the picture below they hadn’t really met up yet and we had a little more filing to do.

However this was really not the point of the experiment but rather to learn and get an answer to a couple of statements I’ve heard from men (yes only men) over the years (continued below picture):

close up of knife edge — This is what an 100 grit knife edge looks like under 240 times magnification

You should only pull the knife over the whetstone – This didn’t matter at all compared to filing motion

You should only push the knife over the whetstone – Well again, no this didn’t matter at all compared to filing motion

You should use a circular motion over the whetstone – Removes material quicker then the windscreen wiper motion

If you start out too rough you have destroyed the edge and it can’t be really sharp again – no you can save it but it takes more grinding with a finer grit then I expected (I suspect this is from using an angle grinder/grinding wheel and thus removing the tempering of the steel by heating it too much)

My findings are that you can do pretty much anything and still get a razor sharp edge as long as you:

Grind away until the edges meet

Use a light touch to avoid pushing the edge to the other side

Switch sides more and more often for the same reason

The edge below is the same as in the first picture but after progressing trough 100, 300, 600 and 1200 grit and then polishing with leather strop to remove the burr. There are still some grooves in the edge from the previous rougher diamonds but the small horisontal ones are 0.015 mm to give a perspective of the magnification.

close up of a sharp knife — This is the edge after 1200 grit honing and leather stropping to remove the burr

As a material for comparisson I took a picture of something we all know as sharp, namely a razor blade. It is a utility blade but brand new and fresh out of the box :

a close up of a razor blade — A utility razor blade under the same magnification

Here is a short video of my expermiments, I hope you enjoy it!
It’s also available here
https://youtube.com/shorts/a9x3c9GRmbA?feature=share

0