Saddle stitching

Saddle stitching is the art of inserting forms on top of other forms, over a saddle and driving stitches through the gathered backbone. Stitched products lie flat and can be economically produced in nearly any quantity. Many other inline bindery operations may be combined with saddle stitching for efficient production.

Technical Tips

All signatures should have the same pre-trim size (head, foot and face). Avoid weak, oversized signatures, which will be crushed when joggers attempt to position the product for final trimming.

When stitching accordion folded, gate-folded, 6-page foldout or unbalanced signatures, glue is needed to keep forms from unraveling or falling off the saddle chain. Your layout should include a minimum of 3/8” (ideally 1/2”) re-trim area so that the glue will be completely removed by the trimming process.

Unbalanced signatures may require special handling to keep from falling off the saddle chain. Special machine rigs may also be needed.

When refolding relatively thin jobs against the backbone, plan for the stitchers to “stagger” after refolding. When folding against the backbone, stress on internal and external pages increases with product thickness, which results in more wrinkling, gusseting and possible tearing of the backbone. Folding saddle-stitched products either with or against the backbone produces washout (aka pushout) and should be discussed with your customer in advance.

Saddle Stitching Spoilage

The balance between consuming more paper and press time than absolutely necessary and providing appropriate bindery spoilage allowances is one of the most difficult parts of the graphics arts estimating and production process.

Graphic Finishing Industries of Illinois publishes a document called “Guidelines for Normal Spoilage Allowance.” We can recognize that these guidelines may be considered “generous,” but nonetheless, we believe that they are a good starting point. If you need to reduce the suggested spoilage allowances on a job-by-job basis, you will probably be okay most of the time. However, we highly recommend that you discuss your jobs’ spoilage requirements with us in advance for all but the most routine jobs.

Graphic Finishing Industries Normal Spoilage Allowance Guide

Because spoilage occurs in every bindery operation, your finisher needs sufficient print overruns in order to deliver full counts. The following spoilage guidelines were developed by the Graphic Finishing Industries of Illinois to help customers plan print production. Please bear in mind that these guidelines will not cover every job, so check with us first.

Insert/Stitcher/Trimmer

(Normal job on paper stock of 45# coated up to 100# coated).

1 pocket…2 per cent
2 pocket…2.25 per cent
3 pocket…2.75 per cent
4 pocket…3 per cent of the finished count, plus 500 signatures for make-ready

Of the finished counts plus 500 signatures for make-ready

Example: 500,000 finished books of four signatures. Spoilage allowance 15,000 of each signature, plus 500 (four signatures with binding laps; 4 pockets = 3 per cent of 500,000 finished books = 15,000, plus 5000 for make-ready = 15,500).

Saddle Stitching Spoilage- Part II

For saddle-stitched jobs requiring five or more pockets (up to 12 pockets), add 0.25 per cent more spoilage per additional pocket. For example, if you have a nine-pocket job, our normal recommended spoilage allowance is 4.25 per cent plus 500 of the finished count, plus 500 signatures for make-ready.

When your customer specifies “no unders,” the rules change. In these cases, it’s much better to err on the side of conservatism than to risk going back to press.

More Graphic Finishing Industries recommended spoilage percentages

1 per cent per vacuum-fed signature
1.5 per cent for one-up oblong books
0.5 per cent for all two-up jobs
2 per cent for 4-page signatures of 50# book weight or lighter
0.5 per cent for each 8-page signature
2 per cent for jobs on uncoated stock lighter than 45#

Additional Guidelines

The following factors could adversely affect these spoilage guidelines:

• Condition of material as it is packed on pallets or skids going to finishing operations
• Numerous lots or codes
• Allowable overrun is an important part of the target figure; therefore, when a “no under” run is allowed, an additional 10 per cent beyond expected spoilage must be delivered to the finishers on most jobs.