RIP Dr. Vadim Kraichuk of Knife Grinders Australia

Status
Not open for further replies.
Sorry to hear about Dr. Kraichuk. I didn’t know him, but I did read his book: Knife Deburring.

He had a lot of interesting ideas, so maybe as a tribute we could discuss some of them.

Here are a few:

The best edge geometry for a long lasting edge is 10 degrees per side (DPS) for high-quality knives. Thinner edges stay sharper longer, provided you don’t damage them.


Toothy edges that so many here like do not cut better. The deeper scratch patterns of toothy edges are easily damaged, leading to poor performance. The initial bite is impressive, but the toothy edge will dull fast.


Convex edges work well for chopping, but the V edge is better for most EDC tasks. They dull faster and are prone to slipping when cutting. [My own opinion is that you have to specify the exact characteristics of a convex edge, which can be more obtuse, less obtuse, more robust or less robust or almost exactly the same as a V edge.]


Stainless steel have better edge retention than carbon steels.


There are layers to the burr edge. The root burr — the first layers in the creation of a burr — is the hardest and most difficult to remove. In fact, the micro-hardness of the burr root is harder than the base metal. [I’ve found that very short, edge-leading strokes will quickly remove a burr and root burr, but trying to strop it off is a waste of time. Stropping works best (refinding an edge) on an already sharp, and clean (deburred) edge.] He says that if you try to strop a burr with bare leather, it won’t come off.


High-rpm honing reduces edge wear. Belt sharpening can reduce edge hardness by 5 Rc. Heat softens the edge.


Knives will spontaneously lose sharpness after sharpening. Oxidation, even with stainless steels, can widen the edge apex in the first two hours. An over-thinned apex can bend during the next 10 hours. This effect is greater for softer steels. Harder steels do better.


He characterized sharpness by the width of the apex.

More than 1 micron is a dull knife.
A working edge is 0.7 microns.
A sharp edge is 0.5 microns.
Shaving sharp is 0.3 microns.
Razor sharp is under 0.1 microns.
Tree topping is 0.05 microns.
 
I read his book, too, and I agree with most of what he said, with the caveat that his company mostly sharpened knives for the food prep industry so that's the area where most of his experiments were focused. His discussion of stropping angle was interesting, suggesting that it's better to strop very high wear steels at a lower angle than the sharpening angle, where softer steels benefit from a higher angle.

Regarding belt sharpening, he did make a distinction between high speed and lower speed grinding, with the latter having less impact on edge retention. His company uses variable speed grinders with paper wheels and/or rock hard felt for deburring, and even sharpens some knives on bench grinders with CBN wheels, using their own cooling compound.

Whatever you think of his theories, there's no denying that he was able to get knives SCARY sharp with his methods.
 
Status
Not open for further replies.
Back
Top