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[BKARTS] Double-fan binding perfect bound books

Hi Waqar:

Duncan is right that some binderies do use notches when double-fan binding.
In my opinion notching is not necessary with double-fan gluing. It appears
that most people doing hand bookbinding using simple double-fan jigs do not
use notching. I would guess that most high volume production double-fan
bindings do not use notching either. I have opened many such books and there
are no notches visible. Yes I see very slight notching in lay-flat
polyurethane bound books, but these are not double-fan glued.

The double-fan binding already has up to 2 x the strength of normal perfect
binding using hot melts and up to 2x  the strength of a sewn binding when
using non coated paper. Notching 1/4 to 3/8 inches deep seriously reduces
the flexibility of the binding. It is possible to increase the depth of the
glue line and thereby the strength in double-fan gluing by rather increasing
the fan angle. It could be increased to 180 degrees if necessary. This is a
way of increasing the strength even more on thick volumes without reducing
the flexibility as much. At least these are my conclusions after
considerable experimentation, pull tests, and bending tests.

Modern perfect binding is even going away from deep notching. Older books
were bound using hot melt adhesives which harden very quickly. Many high
speed perfect binding lines use polyurethane adhesive which hardens slower.
Polyurethane adhesive is also much stronger than the regular hot melt
adhesives. It appears that some roughening and slight notching is still used
here. Break open an old perfect bound book and you will see deep notches,
while on polyurethane bound books the notches seem much shallower. The
notches are quite visible in a RepKover polyurethane bound book even though
they are very shallow. The notch depth seems to be only about 0.010 inches
or 0.25 mm maximum.

Double-fanning was invented as a scientific advancement over notching. It
makes sense to slightly tip or glue the sides of the pages together at the
binding end instead of making deep grooves in the paper every quarter inch
or so. Notching hardly increases the area of the glue line. Putting adhesive
on each side dramatically increases the glue area. Anyone with different
conclusions based on facts is welcome to state their case.

Ben Wiens...applied energy scientist
Ben Wiens Energy Science Inc.
8-1200 Brunette Ave. Coquitlam BC V3K1G3 Canada
E-mail: ben@benwiens.com
Energy Website: http://www.benwiens.com
Read my popular web-booklet "The Future of Fuel Cells"

-----Original Message-----
        From a mechanized point of view, the perfect binding machine
has a milling station that puts small crosshatch marks on the spine
as the text block travels past.  Fan binding machines usually have
deeper notching to allow for further penetration of the adhesives.
Some of the notching systems will go as deep as 1/4 to 3/8 of an
inch.  The milling stations on a perfect binder usually cut no deeper
than one or two millimeters.

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