23.1 FOREWORD
Rigging screws and turnbuckles are used to facilitate the tensioning and fine adjustment of length in lifting assemblies and stays where chain, wire rope or textile elements form the main component of the assembly. They can also be used on their own for some applications. Further uses include cargo restraint, suspension, etc.
There are two distinct types:
Rigging screws, which have a tubular body, with threads in the range 6mm – 100mm;
Turnbuckles, which have an open drop forged body, with threads in the range 6mm – 72mm. The standards require rigging screws and turnbuckles used in lifting applications to be proof-load tested and stamped with the working load limit.
US Federation Specification FF-T-791b, Type 1, Form 1 also details a range of turnbuckles in the range ¼” – 2¾” (0.25” – 2.75”) for such lifting applications.