Coil Binding Glossary: Everything You Need to Know

Coil binding, also known as spiral binding, is one of the most popular and versatile document binding methods available. Whether you're new to binding or a seasoned pro, understanding the key terms and components can make it easier to select the right machine, supplies, and techniques for your project. This glossary breaks down the most common coil binding terms — from pitch and coil diameter to disengageable dies — so you can confidently navigate your binding options.

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Spiral Binding

Spiral or coil binding is a popular document binding method that uses durable plastic or metal coils to hold pages together. The coil is inserted through a series of evenly spaced holes punched along the edge of the document, then crimped at the ends to keep it securely in place. This allows the bound document to lay completely flat when open and even rotate 360 degrees for easy reading, writing, or copying.

Spiral binding is widely used for:

• Presentations
• Reports
• Workbooks
• Manuals
• Calendars

Key benefits of spiral binding include its flexibility, professional appearance, and durability. Coils come in a variety of colors and sizes to match different document thicknesses and styles.

Coil Binding Machine

A coil binding machine is an all-in-one device used to punch the holes and insert the spiral coil. Machines may be fully manual, electric, or a combination of both, with features like adjustable punching dies, electric inserters, and built-in crimpers depending on the model.

Manual vs. Electric Punch

• Manual punch machines require you to pull a handle to punch holes through the paper. They’re great for light to moderate use.
• Electric punch machines use a motor to punch holes automatically, reducing effort and increasing productivity — ideal for high-volume or frequent binding jobs.

Coil Binding Supplies

Coil binding supplies include all consumable products needed for coil binding: spiral coils (plastic or metal), coil crimpers, and pre-punched covers or sheets. Many users stock different coil diameters and colors to accommodate a variety of projects.

Spiral Coil

In binding, a spiral coil, coil, or color coil is the plastic or metal spine used to hold the pages of a document together. It is easy to see how they got their name, as they are one continuous spiral. Coils are flexible, durable, and come in a variety of colors and sizes to match different projects. Plastic coils are the most common, but metal coils are available for a more premium or heavy-duty finish.

Pitch

Pitch refers to the spacing between the holes punched along the edge of a document for coil binding. It’s typically measured in holes per inch. The most common pitches for spiral binding are 4:1 pitch (4 holes per inch) and 5:1 pitch (5 holes per inch). More than anything, the pitch determines the look of your document. If you prefer a tighter coil, then go for a 5:1 machine, otherwise, a 4:1 should suit you fine. No matter which pitch you choose, you will need to ensure that your spines match. The correct pitch ensures that the coil easily threads through the holes and allows the document to turn smoothly.

Coil Diameter

Coil diameter is the width of the coil used to bind a document, usually measured in millimeters or inches. The diameter you choose depends on the total thickness of your document. Standard coil diameters range from small sizes (6mm or 1/4") for thin booklets up to larger sizes (50mm or 2") for thick manuals. You can check out our size guide to figure out what coil size will fit your project.

Binding Capacity

Binding capacity refers to the maximum number of sheets a coil can hold. It depends on the coil diameter and the thickness of the paper. For example, a 1/2" coil may hold about 90 sheets of standard 20 lb paper, while a 1" coil can hold around 265 sheets. Always consult a capacity chart to match your document size to the correct coil diameter.

Similarly, your machine may have its own capacity. It will have a punch capacity, referring to how many pages it can handle in one pass. If it has a coil inserter, it will also have a binding capacity that refers to the maximum coil size it can handle. The good news is that if your coil exceeds your inserter, you can still manually twist in your spine to finish the bind.

Binding Edge

The binding edge is the side of the document where the holes are punched and the coil is inserted. For standard coil binding, this is usually the left edge of the document.

Open Throat

An open throat punch allows larger sheets or oversized paper to be punched by letting the paper extend beyond the edge of the machine. This design makes it easier to punch custom-sized documents or create professional edge-to-edge hole alignment. Simply punch one side, flip around, and punch the other. Note if your sheet is more than double the punch length, you will have an empty area in the middle and require two separate spines.

Coil Inserter

A coil inserter is a machine that’s designed to automate the process of twisting coils through the holes of your project. They spin the spine through the punched holes quickly and evenly, with the help of rotating rubber rollers that grip and drive the coil into the document. Coil inserters save time and effort, especially when binding larger volumes. Some punches come with a built-in inserter, but they can also be purchased separately for extra efficiency and versatility.

Coil Crimper

Crimping pliers look just like a regular pair of pliers. They’re used at the end of the binding process to trim and bend the coil. This helps secure the binding so the coil won’t spin out of your document. Some coil binding machines come with crimping pliers or even electric crimpers, but they can also be purchased separately.

Disengageable Dies

Some coil binding machines come with disengageable dies. These dies can be engaged (or disengaged) so you can produce different hole punch patterns for various sizes of paper. Without them, when punching non-letter-sized paper, you may risk partial holes being punched at the edges of your document. Machines with disengageable dies offer greater flexibility for different binding projects.

Punching Margin (Margin Depth)

Punching margin (or margin depth) is the distance between the edge of the paper and the line of punched holes. Adjusting the margin depth helps prevent pages from tearing out of the binding and can help with smooth page turning. Thicker books generally require a larger margin depth to maintain durability.

Oval Holes

Oval holes are an alternative to the typical round ones for coil binding. Many professional machines use oval holes (typically 4:1 pitch) because the slightly wider shape makes it easier to insert coils, especially for thicker documents.

Spine Former

A spine former or binding sleeve is a tool or feature built into some coil binding machines that gently curves the document’s spine before coil insertion. This pre-formed curve matches the natural shape of the coil, making insertion easier and reducing coil snagging on thicker books.

Need More Help with Coil Binding?

At MyBinding, we know spiral binding inside and out. If you have questions about choosing the right coil binding machine, supplies, or troubleshooting your setup, our team is here to help. Explore our full selection of coil binding machines, supplies, and expert resources to get the perfect finish for your next project.