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.
Steel Manufacturing Blog: Keeping it Steel
Grinnell Standards are a way of limiting the variables when designing a clevis rod or turnbuckle rod. While clevis rods and turnbuckle rods can be manufactured in any diameter and set of specifications, keeping it simple is always desirable for the structural steel fabricator. The main structural concern is tensile strength. Round bar diameter is the primary feature that controls tensile strength and the remaining components are designed around that.