20mm Spiral Binding Coils

Diameter determines document capacity, while pitch determines whether the coil turns align with the holes. Standard plastic coils of this size commonly use a four-to-one pitch, meaning four holes per inch. A correctly sized coil will still be unusable if the document was punched for another pitch. Confirm the machine specification or count the holes across a known binding length. Hole shape may also matter because round and oval patterns can behave differently during insertion. Keep the paper guide fixed across every punch lift so the pattern remains continuous. If covers are punched separately, use the same edge setting. Matching pitch and alignment prevents the coil from binding midway through insertion or placing uneven pressure on the holes.

Larger diameters can require more control during insertion because the coil has a wider curve and the document stack is thicker. Electric coil binding machines can combine compatible punching with a powered roller that feeds the coil more consistently than hand insertion. Confirm the machine pitch, maximum document thickness, punch width, and roller design before choosing equipment. Even with powered insertion, the first few turns should be aligned by hand so the coil enters the holes correctly. Jog the document square and use a spine former when available. Electric assistance is most useful for repeated production, while occasional work may still be manageable with careful manual insertion.

Yes. A coil is usually longer than the binding edge so there is enough material to center, trim, and crimp both ends. Place the document in the middle of the coil with a similar amount extending beyond each end. After insertion, cut and bend the ends inward so the coil cannot rotate out. Do not trim it flush before forming the crimp because the inward bend is part of the secure finish. Coil length and coil diameter serve different purposes. Length must cover the binding edge with finishing allowance, while diameter must fit the document thickness. For custom sizes, confirm that the supplied length provides enough excess at both ends without creating unnecessary waste.

Coil crimpers cut the excess plastic and bend each end inward. This prevents the coil from rotating out of the document and removes sharp, unfinished ends. Coil binding crimpers include hand and powered options for different production levels. Use the tool in the correct orientation at the top and bottom so both ends bend toward the document. Ordinary scissors can shorten the coil but cannot form a dependable crimp, which may allow the binding to loosen during handling. Practice on a spare coil before finishing a large run. A clean crimp should be secure, smooth, and positioned far enough from the first hole to allow free movement.