Bar Product Terminology and Finish

The terminology used for bar products is occasionally misunderstood. General requirements, such as those for tolerances, marking, packaging, etc., are standardized in ASTM A484 for stainless bar products.

For aerospace standards, dimensional tolerance requirements are in AMS 2241.There is no ASTM general requirement standard for nickel alloy bars and all requirements are contained in the individual product specifications.  AMS 2261 contains dimensional tolerances for aerospace nickel alloy bar products.

The terms “cold finished”, “cold worked” and “cold drawn” have different meanings. Cold finished products have tighter dimensional tolerances than those applied to hot finished products. Cold finishing could be any one of many different processing techniques that results in tighter tolerance control.  The statement on finish in A484 is below:

Stainless Steel Bar8.1.3 Cold-Finished Bar—Cold-finished bars shall have the surface finish that results from hot-finished bars being further processed by additional mechanical operations on the surface of the bar, including but not limited to light cold drawing, burnishing, centerless grinding, and polishing to provide closer tolerances and improved surface finish. The dimensional tolerances applicable to cold-finished bars are more stringent than those applicable to hot-finished bars.

Cold drawing is a specific process that causes a significant reduction in cross section and actually work hardens the material.  In most cases, this cold drawn product is annealed, but some specifications do require the material to remain in a strain hardened (or “cold worked”) condition. Cold drawing is not the only method of achieving a cold worked condition.

Stainless Steel Bar BasketExcept for centerless ground product or a specifically ordered polished finish, minor scratches are permitted provided they can be removed while remaining within the permitted tolerances. This is not directly stated in the standards, but would be consistent with the standard Workmanship paragraph from ASTM A484 below:

10.1 The material shall be of uniform quality consistent with good manufacturing and inspection practices. Imperfections shall be of such a nature or degree for the type and quality ordered, that they shall not adversely affect the forming, machining, or fabrication of finished parts.

This statement allows that it is quite possible to have a few scratches on a burnished or cold finished and pickled surface that was made well within the bounds of good standard practice. Note that 10.1 does NOT list appearance as a valid criteria. It is all directed toward addressing the issue of basic functionality and a quality consistent with the method of manufacture.

ASTM and AMS standards are copyrighted documents that are available at a nominal fee at the respective websites: www.astm.org and www.sae.org.