A wire comb is the name of the actual metal part of a wire-bound book. These bindings come in a variety of sizes and configurations. In most cases, a wire comb is made of metal, but it is occasionally made of plastic. Metal wires are the preferred method of binding, as they hold their shape well and can resist impacts that would deform or break other materials. Unlike many book-binding methods, using a wire comb is usually very simple, and machines run from large industrial binders down to personal ones small enough to fit on a bookshelf.
There are two common wire comb styles. The 3:1 pitch comb has three holes per inch or meter. This tight comb style is common in small books or personal document binding. These combs are often double-wired, meaning there are two wires going through each hole.
The similar, but more widely spaced, 2:1 pitch comb is more common in mass-produced books. These combs may be double-wired, but it is just as common for them to be single. Outside of the number of loops per inch or meter, the main difference between the two and three pitches is overall size. The three pitch is used in smaller books, and the two pitch is used for larger ones. Both the 3:1 and the 2:1 systems work in round or rectangular holes.
There are several other styles of combs on the market that don’t conform to these two ratios. In general, these combs are proprietary systems that work with specific machines. A common example of that is the 19-loop spiral. A 19 loop is designed so there are 19 holes in the binding; smaller books have tighter holes, while larger books have them more widely spaced apart. This system was a very common size and style for many years, but has somewhat decreased in popularity in favor of industry-standard varieties.
Wire combs typically come in two varieties—the spiral and the clasp. A spiral is the kind used in most simple books, like notebooks and personal planners. Clasps are not wound like a spiral; they close around the book like a clamp. Spirals are usually single-wired and round-holed, while clasps are usually double-wired and rectangle-holed.
There are two main methods used to bind books using a wire comb. The industrial version typically uses a large binding machine that operates on an assembly line. These machines will use both spiral and clasp bindings and are almost always industry standard. Personal wire-binding machines are small and portable, allowing people to bind books at home. These systems are just as likely to use a proprietary system as a standard and favor clasp bindings over spirals.