HeliCal Wire Inserts:
HeliCal wire inserts provide positive means for protecting and strengthening all tapped threads. They are mirror-smooth, reinforced internal threads of cold rolled 18-8 stainless steel, of hardness 43-50Rc, or other specialized material, with hardness for in excess of the usual tappet materials. The outstanding engineering features of HeliCal inserts have established their widespread use in the fields of aerospace, industrial and military equipment manufactures. Maximum design flexibility as well as compliance with conventional engineering practice gives the designer unlimited opportunities to use HeliCal inserts assemblies. Five lengths of insert for each thread size are available, lengths of 1, 1.5, 2, 2.5, and 3 times the normal thread diameter. This choice of insert length offers the designer the opportunity to balance the tensile strength of the bolt against the shear strength of the parent material. The variety of insert lengths also aids the designer to conform to the conventional engineering practice of assuring bolt failure rather than damage to the parent material when the assembly is subjected to destructive loads. A table has been prepared to assist the designer in choice of thread engagements for different combinations of bolt and parent material.
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