Time spent grinding is relative to how accurate each pass is and how difficult the geometry of the blade is. I think that makes sense.
I've spent almost twenty years at the grinder learning by making mistakes and then developing techniques that correct these mistakes. I live so far out there was no opportunity to learn under the tut-ledge of an accomplished knife maker. I think it's known as the hard way.
While learning to make knives, I found if you watch closely and interpret what the problem is, you will find an answer. This sounds obvious I know; but this is what made Leonardo Da Vinci what he was; observing and then developing techniques that will result in the desired effect. If you want to create a Mona Lisa or The Last Supper, then watch closely, what is being done in front of you.
If I am grinding a proto type, a first, I'll grind it "free hand" to see where the problem areas are. If I end up grinding the blade again, I'll do it with a Bubble Jig with specific set of angles and with a grinding clamp that will produce matching plunge lines, with no correction required at the end of the grind. If a third matching blade is needed, then the time required goes down, because the grinding angles are a given and the plunge lines match.
Grinding should not feel like you are struggling with the blade, but instead, you are part of the grinding process.
There is no answer to the OP, there are far to many variables.
The bottom line on grinding blades is " there should not be corrections needed when you get to the grind line at the spine of the blade. The bevels should match, without having to "blend" or convex the bevels
PS. Many of us were frozen to the point of not being able to work in the shop this January. Bethel Ridge Forge is in that column. For all those affected by this freeze; we wish you all the best and hope your machines made it through as well as yourselves.
Happy Grinding, Fred and Kevin Rowe.
I use jig and I can grind FFG 4 inch blade in minute ..........
