Flat grind-Sharpening question

[jefroman]

I read a post a while back that said:
"after you sharpen a flat ground knife a lot, you'll need to back bevel".
What is back beveling? What does it do? The post also said that the reason you do this is because the more you sharpen a flat grind, the wider the edge gets. Is that true?
How do you back bevel? I've never owned or used a flat ground knife before, so I don't have any experience with this.

Thanks,

Jeff

 

[Crayola]

Think of a flat ground blade as a triangle. The spine fo the blade is, say, 3/16" thick and tapers on each side to the middle. You can see that as the edge wears away, the thickness at the edge will get thicker and thicker, all the way up to the spien thickness of 3/16". Of course, you could never get to that thickness! I just hope you can understand what I am saying.

An edge with thick steel behind it won't cut as well, because the steel is in the way. It also makes sharpenign hard, as you have to remove a lot of steel to get a nice thin edge. To back bevel, all you do is take your knife to a rough stone and put it at, say, 15-17 degrees and scrub away. You will thin out the shoulder (the metal behind the edge) and this will allow you to have the two things mentioned above: thin steel behind the edge for better slicing, and a thinner edge area to make sharpening easier. Back beveling isn't precise work. WHen I do it by hand, I get my angle all set and really scrub/rub back and forth, circles, whatever. Just get that steel out of the way.