Pj wrote:
The chimney wall in the kitchen is 17 1/2 inches wide. The tiles are
actually 4 1/4 inches square.

I plan to use bullnose tiles on each end. At one end I would need to
lay in a 3/4 inch piece of bullnose and that's where I see a big
problem.

If I center the first tile in the middle so that the center of the
tile itself is on the center line and use a full bullnose on each end
that would leave me 2 pieces to fill in which would be cut to about 2
3/4 inches. I would sand the cut edges to a small curve.

The layout sounds reasonable. Not sure why you feel a need to "sand"
ceramic tile edges - really isn't necessary if you make clean cuts.

Does this seem reasonable? Is there way to cut off 3/4 inch pieces so
I don't break the tile without using a wet saw; that is, scoring and
snapping.

Cut off 3/4" from a 4 1/4" tile leaving 2 3/4"? Or do you mean
cutting the bullnose?

In any event, the big box stores will cut the tile for you. Go at an
odd hour so they're not super busy, and the tile aisle guy will cut
them gratis.

R