I mean, what is the physical reason to use water/oil? What are the practical differences between soaking it and keeping it dry while sharpening a blade?
In: 8
I believe it’s because as you remove metal from your edge you want that material to be removed from the new edge that you are creating.
There’s alot of little reasons but the main one imo is removing heat from the very tip of the blade as you sharpen it. Heating the edge too much will make it brittle, lubricant dissipates that heat
When you’re sharpening a cutting edge, you are removing bits of metal. Coarser stones remove bigger bits and finer stones remove smaller bits. These bits of metal are called swarf. If you sharpen on a dry stone, the swarf can fill in the tiny spaces in the stone that do the actual grinding, making the stone less efficient. Also, on coarser stones or rougher edges, the resistance of the stone to the blade can cause uneven wear.
tl;dr: To carry away swarf and act as a lubricant for a smoother sharpening stroke.
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