Darrell Clarke asked about zero adjusting the Duo-Art Expression box.
He mentions Michael Kitner's system, which is the one I am also familiar
with in reprint form. I think it's a fine system, frankly. The point
Mike was making although not stated directly is this: The so-called
"Regulator" springs really provide the linearity of the box by being
large in diameter and very long. So the longer you can leave them, i.e.,
the less tightening you are able to give them, the more linear your
response will be.

Mike also agrees that the most important single item about that box is
the wad of felt stuffed into the spill hole. Unless that is right on the
money, you can forget regulating the expression box.

When Duo-Arts have stretched out expression springs, there is nothing
you can do except have more rewound. I have not needed any yet, since
I have a few left from what was once a huge cache of springs taken from 
Duo-Arts that a guy here in town had gutted and stashed. But one of
these days, I will be needing new springs, I'm sure. The problem is the
plating. When a spring is plated, it loses some temper, and when you buy
plated wire, its spring constant is less than ideal. Also, plated wire
is usually cadmium, which is just junk. I would like to find some tin-
plated wire with the right characteristics. So one of these days,
I guess....

Craig B.