'Seeing' sharpness

[redcollective]

Hello Folks,

Read somewhere today about a way of seeing sharpness by looking for the basence pf a glint of light coming off the edge of the blade, but can't find anything about how or what to look for - does anyone know what I'm going on about? Or is this some hair splitting myth? I sharpen until I can shave with the knife after I strop it and run it down a bit of ground glass. What else is there for a measure of sharpness without resorting to the electron microscope?

 

[fa11en ange1]

Hold the knife with the sharp edge facing up while standing under a light. If there are any blunt areas they will reflect the light and look shiny. Where as a sharp blade has no flat surface along it's edge to reflect light, so in effect appears black.

I find it to be a really good method by which to check for bluntness, however the ability to shave and push cut newspaper are about the best ways to test sharpness.

 

[Motorbike Man]

You can always tell when I've been having a sharpening session by the pile of tiny bits of paper around my chair and the patchyness of the hair on my arms generally I'll check with a piece of paper firs, getting the blade to the stage where it will slice through with out any friction at all, and then I'll try the hairs on my arm and if it will shave those easily then that'll do me

 

[Neil1]

I think the book you are looking for is Mors Kochanskis Bushcraft, it has a very good section on sharpening.I have had a copy for many years and the lessons in that chapter have more than prove themselves, I have a japennese waterstone but normally carry a sharpening board in my pack, cheaper, lighter and very effective.
Neil

 

[leon-1]

I use this method with all of my cutting tools as a way to gauge whether I am close to getting round to stropping, I even use it when sharpening my axe

It will give you an idea of if the bladed tool is sharp, but as stated by others there are better tests that can be used for checking final sharpness of a tool.

 

[Hoodoo]

I've found that my "seeing" is helped a whole bunch by a decent 10x loupe.

 

[zambezi]

Hello Folks,

Read somewhere today about a way of seeing sharpness by looking for the basence pf a glint of light coming off the edge of the blade, but can't find anything about how or what to look for - does anyone know what I'm going on about?

I have found the reflection test very useful, not only to ascertain whether the blade is sharp, but also to verify that you are sharpening the blade evenly on both sides.

This is easiest done by wearing an LED head torch on a low setting. Hold the knife with the cutting edge facing upward [spine parallel to the floor] and turn the knife slowly and smoothly through an arc that takes the edge to 45' left and right of the beam of light from the head torch.

If there are any flat spots on the edge, then they will catch the light as the edge passes through the plane that is perperdicular to the head torch. You need to take the knife out of the parallel-to-the-floor plane to view the status of the edge nearer the curve of the blade. I.e. repeat the rocking from side to side motion, but drop the pommel/butt end nearer the floor.

Vince

 

[redcollective]

Cheers all, I can see what it was on about now! The dark centreline really is apparent - and in my case shows up a little uneven grind... back to the stones!