Tensile is defined as the uniaxial tension until failure measured in pounds per square inch (PSI). The higher the failure point the stiffer the wire, this is measured on tensile testing machine. 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 down time. High tensile wire can also 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 saddle stitcher jams. A tensile below 135,000 PSI will cause the stitching wire to be soft and not properly form a proper stitch.
High tensile stitching wires are available in the industry, 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.