Originally Posted by
Wilbur Pan
By the way, I can put a polished surface on this chisel and plane blade with a manmade waterstone, and get a similar shaving. That should show that the polished vs. matte finish really doesn't come into play in determining how sharp a tool edge is.
I have shown people that you can get a usably sharp edge straight from the grinder if you're careful enough and have a set up like I do - very slow speed and fine grit, turners do it every day... Usuably is the key word as there are as many ideas about how sharp a tool is as there are stars in the sky. Basically if the tool cuts to your satisfaction and leaves the desired result it's sharp enough. Have a look at what the Egyptians 2500 years ago were making with tools most of us wouldn't even have in our little hobby shops sometime if you don't believe me. You can bet they weren't too concerned with grades of mirror finish on their tools.
But what you should really be talking about with respect to how "shiny" or "reflective" an edge should be is the relative time it will stay sharp. What you may not have noticed in those micro graphs is the more irregular edge produced on the "less shiny" edge. Those irregularities will break off much quicker and leave you with a tool that no longer has a usably sharp edge. The more irregular the quicker the edge will erode. The same principle applies to using a steel in the kitchen. It literally rips the steel of your knife and leaves it with a very ragged edge, relatively speaking. But it's an edge that will cut through most things in the kitchen extremely well. Because nothing, except bones, are all that hard in the kitchen the edge produced is quite adequate, or as I like to say usably sharp. And will stay that way for an acceptably long enough time. Long enough that there is no reason to go to such lengths as we do to obtain a mirror finish on the edge. In fact that micro serrated edge is a benefit in the kitchen.
Now I have to get back to learning regression analysis...
Sent from the bathtub on my Samsung Galaxy(C)S5 with waterproof Lifeproof Case(C), and spell check turned off!