--- In PPLetterpress@yahoogroups.com, "Michael Babcock" <mjb@...> wrote:
<< The bearers don't affect rail height, they negate the fact that
they exist at all. The overly low height can't be explained away by
wear, nor by a lack of type height standardization. So, there HAD to
have been some kind of device in play that would raise the rollers to
a trued height. Bearers can be the only explanation given that the
rails, at least on my old press are +/- .010" low. Unless crappy
inking was the norm, this would be to great a variance for even compo
to absorb. >>
Your Formica is a smart fix for the problem. Sure beats layers of
softer material, even pressboard.
Wear is absolutely a factor in track height. Whether the tracks were
originally exactly .918" is a question, but I would suspect they were.
The C&P that forced me to refine roller setting had tracks worn
four points below .918" (to around .862"). Not worn evenly either, but
with higher and lower areas, and different from side to side. Every
single platen I've measured (with depth micrometer) since then has had
wear of varying degrees. It is inevitable with 50 to 100 years of
metal trucks wearing them down. Rubber trucks are a later development.
Different forms require different roller contact, and in one Colt's
Armory catalog I once saw (but can't now find), three different truck
diameters were made for adjustment--for example, trucks 1/16" over
roller diameter recommended specifically for rule forms (for light
inking or to prevent roller cutting or both?). So different diameter
trucks are not just for shrunken or swollen composition rollers as is
The manufactured roller bearers I've seen were all intended for
small presses; Kelseys without keyed trucks would seem to require
them. But on larger presses bearers are also used to equalize
impression, as well as control roller height or rotation.
On a Colt's Armory type press (lacking platen levelling bolts), it
was normal to use a bearer to balance off-center forms (a variation is
to use "bumpers" glued to chase and platen).
If it wasn't for the more precise inking demands of photoplymer
plates, we might not even be considering this. Our predecessors did
fine work on worn presses with metal type.
--Eric Holub, SF
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