A Closer Look at Stitching Wire

by: Kris Shaw, WCJ Pilgrim Wire

In today’s commercial printing industry, stitching wire is used in two areas – the bindery and pressroom. Stitching wire is a low-carbon steel with a galvanized or tin coating. Stitching wire is used in the bindery or finishing departments in the form of saddlestitching, bookletmaking, side stitching and corner stitching. A more recent trend WCJ Pilgrim Wire has seen is growth in the use of stitching wire for the pressroom in high-speed web operations in the form of inline stitching.

Stitching wire has evolved as the industry has changed and now is a highly tuned part of the printing world. Quality of finish, size, cast, camber, tensile, path of wire, wire delivery, spool size, and despooling equipment all are major factors in how stitching wire is going to perform in the field. With the continued demand for increased run speeds and overall profit, high-quality stitching wire and proper machine set-up are a must.

Stitching Wire Attributes

Quality of Finish. An ideal wire is chrome-like in appearance with special friction-reducing additives to resist peeling and flaking while providing a superior workability in all bending and forming applications.

Cast and Camber (Helix). Commercially produced, stitching wire is not straight. Each spool size has a desired curvature of the wire. The radial or circular curvature is known as “cast,” which is measured as the diameter of a free turn of wire. The axial component is referred to as “camber,” which is measured at the offset in the ends of one turn of freely hanging wire. A large cast and small camber are characteristics of a high-quality wire. This allows the wire to go into the stitching head smoother, producing less drag and providing fewer dropped stitches. The stitching head will work more efficiently with less energy and maintenance.

Tensile. Tensile is the pull required to break the stitching wire and is measured in pounds per square inch (PSI). The higher the breaking point the stiffer the wire. High-quality stitching wire has a tensile range of 135,000 to 165,000 PSI. A tensile above 165,000 PSI will wear out parts in your stitching head prematurely, causing maintenance costs and downtime. High-tensile wire also can wear out the knives in a trimmer section prematurely. The increased hardness of the stitching wire will nick a trimmer section’s knives more severely when struck during saddlestitcher jams. A tensile below 135,000 PSI will cause the stitching wire to be soft and will not properly form a stitch.

High-tensile stitching wires are available, but the cost benefits of using a high tensile wire with a thinner diameter on thicker applications is outweighed by the cost of premature wear on stitching heads and trimmer section knives.

Path of Wire. A clean path for the stitching wire from the spool to the stitching head is critical in getting a positive stitching outcome. The coating easily can be chipped, scraped and damaged by running the wire past an unprotected steel bracket, worn wire guides, spring tubes and dirty felt pads. These areas must be checked frequently and rotated or replaced on a regular schedule. Wire guide springs and felt pads are a normal wear part on any stitching head. Flat spots on guides and springs, along with a dirty felt pad wiping system, can cause flaking issues that will jam your stitching head, stop production and cause additional maintenance and repair costs.

Types of Wire. Electro-galvanized stitching wire is the most widely used type of wire in the printing industry. Today’s friction- reducing electro-galvanizing process provides a smooth burr-free finish that works well with small-, medium- and large-size binderies and inline web stitching applications.

Tin-coated stitching wire still is used in a small number of binderies and finishing departments. Because of the small number of tin wire users, the cost is higher than electro-galvanized stitching wire. Tin wire adds little or no added value to the stitching process or the stitching head.

The Right Size Stitching Wire for the Job

The majority of the stitching wire used in today’s binderies and inline stitching operations is 24- and 25-gauge. The difference in size from 24-gauge (0.023-in.) to 25-gauge (0.0204-in.) is 0.0026-in. This small amount may seem insignificant, but it means a lot in terms of yield.

A 24-gauge wire has 8,496 inches per pound of wire, and 25-gauge has 10,800 inches per pound. This amounts to a 21.3 percent difference in product yield, which translates into 21.3 percent more staples if you use 25-gauge over 24-gauge. In simpler terms, if you imagine a staple or stitch being one inch, you would have 2,304 more staples by using the 25-gauge wire over the 24-gauge.

Choose the right wire for the job:

  • 25-gauge stitching wire’s recommended thickness of work is 1/16 to 7/32 of an inch.
  • 24-gauge stitching wire’s recommended thickness of work is 1/16 to 1/4 of an inch.

These are only suggestions, as paper type, density, coatings and stitcher set-up can change the stitching wire size required. Physically check the size of your stitching wire and don’t believe what is on the label until you are sure. An oversized wire that is labeled 25 gauge but actually is larger in size means you are not getting what you are paying for. Oversized wire substantially affects the yield of your wire along with increasing the amount you end up paying at the post office.

Location and Inventory of Your Source

Does your wire provider have a facility or warehouse in the proximity of your location? As an extremely heavy commodity, shipping costs are some of the primary contributors to the end price of your stitching wire products.

Weigh out the cost savings of having a localized source and your freight expenditure. Will taking more stitching wire create a bigger savings for you?

Spool Sizes, De-Spooling Equipment and Winding

Stitching wire comes on many different spools and generally ranges from 5 lbs. to 1,600 lbs. Primary usage and machine type determines the size spool you require, but running speeds and space availability also play a role. Standalone stitchers that are hand fed usually use 5- or 10-lb. spools. Collators with stitchers used for short runs of 5 or up to 10,000 books can also use this type of spool. Saddlestitchers for longer, mid-range runs will use 35-, 40-, 70-, or 100-lb. spools. High speed collator/stitchers and web operations using inline stitchers will use 200-, 250-, 1,000- and 1,600-lb. spools. A larger spool of wire has both economical and production advantages. Larger spools cost less per pound of stitching wire to manufacture. Larger spools require fewer spool changes during the manufacturing process.

During the binding process, larger spools prevent stoppages of the line for spool changes, thus increasing your books-per-hour output. A normal spool change averages two minutes per spool changed, and generally a saddlestitcher runs anywhere from two to four stitcher heads at a time. With four stitcher heads running a job of more than 100,000 pieces with 5-lb. spools, you would be stopped for spool changes a minimum of sixteen minutes alone. Changing to a 35-lb. or 40-lb. spool would wipe this changeover time to zero.

Different sizes of spools have different characteristics that can give the end user advantages. For instance, as stated earlier, a larger circle diameter improves the performance of stitching heads with less friction due to less straightening required and fewer dropped stitches. A 35-lb. spool, which is flatter and has a wider diameter, has a larger circle diameter than a 40-lb. spool, which is taller and has a narrower diameter. The larger diameter spools, such as the 200-, 250-, 1,000- and 1,600-lb. spools, have larger circle diameters, improving stitcher head performance since less straightening is required.

Proper de-spooling equipment is essential to complement the high-quality wire used. Matching the correct de-spooler with the spool is essential for problem-free production.

How a spool is wound is important especially when the larger spools (200-, 250-, 1,000- and 1,600-lb. spools) are statically (the spool does not move) de-spooled. When a spool is standing on its end, conical winding (winding that is wider at the bottom than at the top) prevents the wire from “falling” as it de-spools. This can prevent wire tangles and jamming. Conical winding needs to be done very precisely during manufacturing to prevent problems. Smaller spools (100 lbs. and less) do not have to be conically wound in order to de- spool properly.

Straight winding is fine for smaller spools that are dynamically paid off (the spool moves on a spindle) and needs to be done correctly by evenly winding the wire across the spool. The stitching wire can’t build up in an area, as this could cause tangles. Straight winding on statically de-spooled larger spools is helped by the use of a proper de-spooler.

Green Initiatives: User and Producer of Print

  • User. Unstitched flyers, advertisements and newspapers produce more litter. Stitched pieces require only one item to pick up and recycle. Steel staples in recycled paper easily are accommodated by typical recycling facilities worldwide.
  • Producer. Does your stitching wire supplier provide a spool and skid return program? Reusable spools and recyclable products are the way of the future. Throwing away spools amounts to throwing away money in landfill costs.
  • CPSIA. The Consumer Product Safety Improvement Act requires all stitching wire to have less then 100 parts per million of lead content. Make sure you are using a certified stitching wire product. A product recall could be very costly.

Using stitching wire is a profitable binding solution; it has a low cost and gives a high value.

Kris Shaw is sales manager for WCJ Pilgrim Wire. WCJ Pilgrim Wire maintains high standards for the manufacturing of wire through a series of checks and balances, assuring the final product meets and exceeds customer expectations. The company prides itself on the years of experience its employees have in providing knowledgeable advice and recommendations to its customers. For more information, call 414.291.9566 or visit www.wcjwire.com.

Reprinted with permission from the 2012 Forecast Part 2, The Print Production Process, Copyright 2012 by the Printing Industries of America (www.printing.org). All rights reserved.