SL-SF15 Glasses Wire Frame Angle Tester Spring Hinge Bending Durability Test Machine The SL-SF15 Glasses Wire Frame Angle Tester measures the longitudinal force durability of spectacle frame spring hinges. It evaluates the hinge's ability to withstand repeated bending cycles while maintaining original performance, detecting changes in spring force over time. Key Features High Precision: Microcomputer control with LCD display and 0-999,999 cycle counter Flexible Speed: