Yeah, flat grinding can be challenging! I can tell you how I go about it, but everyone finds their own route in the end, for everything we do.
Not to belabor the obvious, but first I cut a 45 degree chamfer along the edge, right to the scribed center lines. This will give a quick visual reference for how close I'm coming to getting the edge thinned out enough. Once the reflection goes away, I'm at the scribed lines.
Next, I put a new 60 grit (or 36 if I'm not so patient) on the 10 inch wheel and do most of the initial stock removal on that. I make a series of parallel grinds, right to the scribed lines at the edge and shallower as you near the spine of the knife. Be careful not to cut too deep! Or you'll just have to start over. The idea is to get the basic form of the grind down with the wheel, which removes a lot more stock with less aggravation than trying to do it on the platen. It will also help to keep your grind from rocking as you lean into the platen next.
Then, with a nice sharp 60 grit belt I clean up the hollows and get the basic shape of the flat grind. This is the time to get the plunge evened up and ensure the grind line is the same height on both sides of the blade. I work back and forth between the sides, keeping them even. Don't get too carried away getting the final shape of the flats, as subsequent grits will still remove a lot of steel. After it's set, I work through the grits.
And yes, I grind with the edge up on both sides. That seems to work best for me, as I can keep an eye on the scribed center lines and eyeball the depth of the grind from the blade's angle against the platen. Also, the spine gives my supporting fingers better purchase than the edge would on the "off" side. It helped me to grind a a slower speed until I got the hang of it...
Don't know whether this will help. The old refrain, "practice, practice, practice!" comes to mind.
Good luck and have fun,
to my left. Flat grinding is harder than it looks. Thanks for all the replies.
