UL 1439 2021 pdf download – Tests for Sharpness of Edges on Equipment.
6 Calibration of Tester 6.1 The sharp edge tester is to be calibrated so that a 1-1/2 ±0.03 lbf (6.672 ±0.133 N) is present at the center of the head when the arm is between stops. The length of the arm is to be adjustable for calibration purposes. See Figure 6.1 for a typical calibration procedure. Exception: Forspecial evaluations, when specified in the end-product standard, the force may be adjusted to a different value. 6.2 The adjustment set screws that hold the pivoted arm in place in the main drum are to be loosened. 6.3 With the handle securely held in a horizontal position, the calibration weight is to be attached to the center of the head. 6.4 The length of the arm within the main drum is to be adjusted so that the weighted arm remains in a horizontal position with the calibration weight attached. 6.5 The adjustment setscrew(s) are to be tightened to securely lock the pivot arm in place within the main drum. 6.6 The calibration is to be rechecked and the weight removed.
7 Test Procedure 7.1 The curved face of the tester head is to be covered with three layers of tape in the order indicated below: a) First Layer (Inner Layer) – Indicating type, black vinyl foam tape as described in 5.1(b). b) Second Layer (Middle Layer) – Sensing Tape No.2, white vinyl foam tape as described in 5.1(c). c) Third Layer (Outer Layer) – Sensing Tape No.1, tetrafluorethylene tape as described in 5.1(d). 7.2 Each tape is to be applied over i a minimum of 90 degrees of the circumference of the test head to prevent stretching of the tape. 7.3 The tapes are not to be stretched when positioned on the head. See Figure 7.1 7.4 The center of the tape-covered head of the sharp-edge tester is to be positioned on the edge to be tested in the manner illustrated in Figure 7.2. The arm of the tester is to be between stops so that the tape- covered head exerts a 1-1/2 lbf (6.7 N) on the edge. The tester is to be immediately moved along the edge a distance of 2 in (50.8 mm) and then back to its starting position without removal of the tester from the edge. It is to then be withdrawn from the edge. The total distance of engagement between the edge and the tape-covered head is not to exceed 4 in (101 mm). The time of travel is not to take longer than 5 seconds nor less than 2 seconds. Exception: An edge less than 2 in (50.8 mm) long is to be tested for a distance of twice its length. (Example: Foran edge 1-1/2 in or41.2 mm long, the testeris to be moved along its length and back to the starting position so that the total distance ofengagement between the edge and testeris 3 in or76.2 mm).