Wire, Spiral, Comb and Post: What Lies Flat

Four bindings let a book lie flat, and they are not interchangeable. Coil takes a round hole and a plastic spiral; wire takes a square or round hole and a formed wire; comb takes a rectangular slot and a plastic finger comb; post takes two or more drilled holes and a screw. Each one asks for a different margin, and each one tears in a different place when it is abused.

What pitch and hole pattern decide

The pitch is the number of holes in the margin per inch, and it is the first thing to fix. Coil is sold in a 4:1 pitch as the trade standard, with 5:1 for very small diameters; wire runs 3:1 as standard, 2:1 for heavy books and 3:1 mini for small formats; comb is punched to a fixed slot count that matches the comb being used. A hole pattern that does not match the element cannot be closed, and punching is the one irreversible step in the whole job.

The punched margin then has to clear the largest tab of whatever is bound in: an index, a divider or a fold-out. A page with a wide printed border and a narrow punched margin is a page waiting to lose its text to the drills.

How much margin does the page need?

Enough to hold the punched edge for the life of the book and to keep the text clear of the holes. The working figure is measured from the trim edge, not from the printed area, and it depends on the element: a coil needs more margin than a wire of the same pitch because the spiral rolls into the hole and the page turns around a larger diameter. Where a book has to be bound in one of these methods and designed tight, the safest move is to fix the paper size first and set the margin from the finished trim.

The second constraint is the block thickness. Coil and wire are sold in diameters; a block that swells past its diameter, usually because the paper took on humidity, will not close, and the bench then has to repunch nothing and replace the element at its own cost. Measure the finished block after pressing, not before.

Which pages tear first

In every one of the four methods the first failure is the same: the page against the cover. It turns through the largest angle, it carries the most leverage, and it does the most work at the punched edge. Coil and wire spread that load over the full length of the margin and are the most forgiving; comb opens in the middle and lets the leaves shift, so the tear starts and spreads sideways; post binding holds the leaves tightly at two or three points and tears in a straight line from the hole.

The second failure differs. On a wire binding the wire itself can be deformed at the ends, and a bent wire catches on whatever is stacked on top of it. On a coil, the coil can unwind out of the end hole if the last pitch is not crimped. On a comb, the fingers snap. Each of those is a repair the bench can do; the torn page is not.

How the opening compares

Coil turns a page a full 360 degrees and lies back on itself, which is what a bench manual or a music score needs. Wire also opens flat and turns back, and holds the leaves more squarely, because the formed wire sits in the holes as a hinge. Comb opens flat but not always square, and the fingers of a wide comb let a thick block sag. Post binding does not open flat at all unless the posts are set loose, and a loose post lets the block shift.

Where the pages must stay in place while the reader works, that difference decides more than the cost per book. A score that will not lie open is a score the player weights with a clothes peg.

What to specify

Name the method, the pitch, the hole size and shape, the element diameter or comb size, the margin measured from the trim edge, and the order of punching and printing. Where the book is punched before printing, the registration is set on the punches; where it is punched after, the block must be pressed and squared first. Name also whether the last holes are crimped, because that is the difference between a coil that holds its end and one that unwinds on the shelf.

Sources consulted for this folio: ISO 11800 on binding materials and methods, and ISO 536 on the determination of grammage for the block weight figures used above.