Stainless Steel Turnbuckle Rods and Clevis Rods have some variations in material that will affect the design and production. The first point to note is the difference in material between the round bar and the hardware. Stainless steel round bar comes in a wide variety of grades. For Structural and Miscellaneous steel fabricating the fundament grade is 303 or 304. Often Clevis Rod and Turnbuckle Rod assemblies are specified leaving the fabricator the option of using either.
The higher grade stainless round bar is 316 or 316L. While there are still many grades above that they are used only for special purposes.
Clevis and Turnbuckle Hardware, on the other hand, is all 316 stainless steel. For assemblies calling for 303/304 round bar the hardware is superseded to 316. This is an efficiency step that allows the manufacturers to limit the range of products they carry and hopefully reduce the cost.
Surface Contamination / Rust
Regardless of the stainless steel grade used for the rod, Turnbuckle or Clevis, the fabricator should be aware that stainless steel contains surface contamination that will rust. This is cause by the tooling used to make the stainless steel. Whether cast, forged or rolled the tools and forms are all carbon steel. In the process of forming the stainless steel, particles of carbon steel wear off and embed themselves in the surface of the stainless steel. Once exposed to the elements these particles being to show oxidation.
To prevent surface rust from occurring the stainless steel Clevis Rod or Turnbuckle Rod Assembly should be pickled, passivated and electro-polished. Or in simple terms, thoroughly cleaned and treated so the outer surface is more resistant to reactions. This includes the Stainless Steel Clevis Pin.
Grinnell Standards
Grinnell Standards are a set of dimensions that can be used as “standards” by the designer of the Turnbuckle Rod or Clevis Rod. They are intended to simplify the process of specifying and manufacturing Clevises by limiting the endless combination of variables to a few practical combinations.
To view the Grinnell Standard Clevises, click here:
For the manufacturer of Stainless Steel Clevises and Turnbuckles the advantage of following Grinnell Standards is limited because the hardware is not made in large lots but is more made to order. Nonetheless the Grinnell Standards are still very useful to the Engineer in that the capacities of each component remain consistent.
Note: All load bearing Clevis Rod and Turnbuckle Rod Assemblies should be designed by a Licensed Engineer.
