Do I understand science behind shaving sharp knife correctly?

[3D Anvil]

has anyone looked at the temperature of the steel right at the apex during sharpening / steeling / honing? is that even possible?? i'm aware of the existence of work-hardening, and from what i've read recently, understand that speed and pressure of honing makes a difference - and both those would have an effect on temperature.

i wonder what would happen to a blade that was kept in a freezer for a while before sharpening / steeling / honing???

Yep, someone has looked at it -- namely the late, great Dr. Kraichuk of Knife Grinders Australia.

Here's the summary of his tests, but if you check his channel you can find the individual experiments.

 

[docflash]

amazing!! lots of good info there. i especially liked the info on what's safe & not safe.

so if a parking lot trailer says "KNIFE SHARPENING" and the person's using a dry stone, just keep walking. good info.

it was interesting to read the paper wheel system w/ silicon carbide & slotted paper wheels heated things up when used as directed . . .

thanks!

 

[me2]

Hello,
I am what would you call a beginner in world of knife sharpening although I never really had any problem with angles. I learned sharpening on gardening tools and I can bring them to quite decent edge (and I also learned to love carbon steel by sharpening them).
I noticed some chips on TOPS CAT yesterday so I decided to buy some 1200 grit sandpaper and repaired and resharpened the edge to be quite sharp. It cuts paper like butter. I would say that it's somewhere between decent and superb sharpness, but I would like to have an edge that can shave without damaging the skin with too much problem. So I went on the internet and started to learn about how to achieve this insane level of sharpness. There are some tutorials that require you too have too much equipment in my opinion, so I summed what I've found below and I will be happy if I could discuss each thing with you.

1) You can definitely produce mirror polish or near mirror polish edge with lower grits, because it has got to do more with pressure than grit, but it will still be better to work with higher grits because in terms of reproducibility. Mirror polished edge is way better speaking in terms of push cuts, so it is more useful for knives you use for cutting things like vegetables or meat.

2) You also don't need to use higher grits for achieving shaving sharp knife, because it's matter of two sides of the edge meeting in one line, so it's matter of properly making the burr more than anything.

And lastly maybe the most controversial statement.

3) You can produce more of a convex shape edge by hand sharpening so it should be more benficial to sharpen by hand than sharpening with sharpening systems or electric sharpeners.

Mirror polishing isn’t needed for arm shaving edges. I’ve gotten arm shaving edges with a coarse and fine file and some of the scariest edges I’ve made were with the coarsest grits like a DMT blue coarse stone. Arm shaving starts when the edge width gets down to a couple microns, 0.002 mm or so.

Avoid uncooled power sharpening. It can produce a sharper edge but it’s extremely difficult to avoid overheating the steel at the edge.

I have not found hand sharpened edges to be superior to jig sharpened ones, but I have not explored edges in a long while. I can get sharper edges with a jig than freehand but not by much.

 

[damib]

Mirror polishing isn’t needed for arm shaving edges. I’ve gotten arm shaving edges with a coarse and fine file and some of the scariest edges I’ve made were with the coarsest grits like a DMT blue coarse stone. Arm shaving starts when the edge width gets down to a couple microns, 0.002 mm or so.

Interesting. Do you also know the approximate width of paper cutting edge? Or how much width of the steel gets removed from the edge with let's 200 grit?

 

[me2]

I do not know but I’d guess about 5x that of a shaving edge for just slicing paper. I once tried to cut cardboard with a cheap knife until it wouldn’t slice paper. I gave up after over half a mile of linear cuts in cardboard.

I don’t know how much gets removed in a pass on a coarse stone. I do know that careful sharpening of a dull but maintained edge will reduce the width of the blade from spine to edge very slowly. I tried on a RADA Cutlery knife and it would take years of weekly sharpening to reduce the width noticeably without having to take measurements.