Description Brother / Jack Check Spring Standard 145519-001 Brother Standard Industrial Sewing machine Check Spring. Part No 145519-001 Also fits many Jack Standard Lockstitch Machines The idea of the check spring is to check the cotton as it goes around the sew mechanism of the sewing machine. The check spring allows for the tension of the thread to be lighter with in the sewing cycle, so helps considerably with pucker on lighter fabrics. The check spring is a vital component when it comes to achieving a balanced stitch on the item you are sewing.
