Spencer Chase asked about the hole distances on a Duo-Art trackerbar.
This is the standard trackerbar, using the printer's scale stick called
pica. It is exactly 9 to the inch. Very easy to duplicate, once you
know the incremental source. More difficult would be trackerbars like
Wurlitzer made. An error of only, say .002 inch per hole (half the
thickness of a human hair) could possibly accrue to an overall error of
about 3/16 inches in 100 holes if allowed to multiply (like leading).
This is why the laying out and indexing of a die for a trackerbar must
be very precise.

Craig B.