An experiment exmined the influence of sewing speed on stitch formation in a lockstitch sewing machine. When the machine was set to a static stitch lenght of 3.1 millimeters, the location of the interlacing point shkfted upward and the stitches became tighter as sewing speed increases. This phenomenon was attributed to the dependencies of tightening tension and feed length on needle and bobbin thread tightening ratios. Incrases in tension tended to reduce the needl thread length -- making the stitch tight. In contrast, when the machine was set to a static stitch lenght of 2.0 millimeters the location of the interlacing point shifted downward as the sewing speed increased past 2,000 stitches perminute. The researchers attributed this phenomenon to the influence of sewing speed variation, the magnitude of which was much greater than the dependencies of tightening tension and feed length on neelde and bobbin thread tightening ratios. 3 refs.