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On earlier models of hedge trimmers, the cutter blade retaining bar assembly was attached to the stationary bar with (5) five 8-32 x ½” hex head machine screws and nuts. The nuts were crimped for locking action. A spacing washer between the stationary bar and the retaining bar allowed the cutter bar to reciprocate. The continuous vibration of the machine screw and crimped nut resulted in a loosening of the assembly. Also, the screw and nut had to be disassembled to sharpen the trimmer blade. The crimped nut lost most of its locking ability after reuse.
(5) 8-32 x 7/16” hex washer head steel TAPTITE® screws, cadmium plated, were driven into a 0.147" diameter pilot hole to assemble the cutter bar to the steel stationary bar.
The hedge trimmer blade represents an excellent TAPTITE® thread rolling screw application. Break-away and prevailing back off torques of TAPTITE® screws are more consistent than those of machine screws with crimped nuts. TAPTITE® screws in this application provide an excellent strip-to-drive ratio of 5 to 1. Total in-place cost savings are realized by completely eliminating the crimped nut assembly and greatly reducing assembly time. The same TAPTITE® screws can be reinstalled when the blades are serviced without losing any of their original locking ability.