Two horizontally opposed and movable clamping jaws, which hold a specimen 100 mm (4 in.) long under variable tension during the folding cycle, while a slotted folding blade, sliding back and forth between four creasing rollers, folds the paper at 105-125 double folds per minute. The clamps are supported from below on rollers and, while in motion, are freely suspended between tension springs. The folding blade is 0.50± 0.0125 mm (0.020±0.0005 in.) wide, the slot extending somewhat above and below the normal position of the test specimen.
The vertical edges of the slot are cylindrical with radius equal to half the thickness of the blade. The four creasing rollers, each 6mm (approximately ¼ in.) diameter and 18 mm (approximately ¾ in.) long, are arranged symmetrically about the mid position of the folding slot and are provided with antifriction or jeweled bearings.
6 digit mechanical Counter, to register the number of double folds and to stop the instrument when the specimen breaks with reset knob to make it zero.