Kevin,
I started out with the old profile kinves. They can be ground so that
they have the spear point on them like the newer knives, but there is
one bigger change that they made that you can't compensate for. On the
older profile knives if you look at them, you will notice that the
inside edge of the knife is in the same line as the inside curve of the
blade. There is an ear on the outside edge that sticks out farther
than the blade. The cut needs to be wider that the blade to prevent
binding, and if you have ever tried to do a deep part on a spindle in
only one pass, you know all about that. On the newer blades, if you
look at one, you will notice that the cutting tip sticks out on both
sides on the blade rather than only on one side. It centers on the
cutter, rather than being on one side. This makes a huge difference on
the tracking ability of the cut. I would guess that by now you have
noticed how as the cut progresses, the blade wants to track to the
outside rather than stay on the line you are trying to cut. All of the
coring systems with curved blades do this to some extent. The straight
blades aren't as prone to do this. With the new profile blades, you can
actually correct some on the inside of the cut, while with the old
blades, this was impossible without starting a whole new cut. The new
profile does not take a smaller cut than the old blades. The cutter on
the medium set is about 3/8 inch wide. With the spear point, this makes
for about a 1/2 inch wide shaving. With the old knives, I experimented
with bevel to the inside, bevel to the outside which is how they come,
and square. I haven't been able to grind concave. On the newer set, I
tried the spear point, and convex. None of these made any difference on
the tracking ability of the blade as you cut. I grind all of my blades
square now. This does make for a smaller shaving, and a bit less
pressure on the blade as you cut. My recomendation, especially after
converting, would be to buy the new profile blades as they are easier
to manage. Mike Mahoney uses the spear point very well, so changing the
profile may or may not work for you. It isn't recomended by the
manufacturer, but in my quest to make the tool work for me, I just
couldn't resist tinkering. I think that there is a bit of that in all
of us. The only other thing that I did different, was to lock the
gate/fingers in place, and not let them move while I core. Again, this
may or may not work for you.
robo hippy