I have seen the abbreviation “ WMM” used in the metals industry can you tell me what the abbreviation WMM means and more about it?
Well, it means “ waive the method of manufacturing” and it came about years ago because most of the standards in the USA were written for sand castings and new methods of manufacturing like centrifugal casting and continuous casting were proving themselves as better and more economical methods of manufacturing. I mean way back in time like prior to WWII there were specs like the US Navy’s spec 46B23e which today is C83600 or Federal Spec. QQ B 691b which was also C83600. Most drawings back then had these specs as the required material and there were companies that wanted to substitute the better made product that were not sand casted. To communicate to the customer that the material met their specs like QQ B 691b but was not sand casted but was continuous cast the term waive the method of manufacturing became popular. It meant that we met the chemical and mechanical requirements of the sand casting but instead of pouring the metal in a sand mold it was centrifugally or continuous cast. Today the term is becoming popular again because of the alloy C63000 to the standard AMS 4640 which is an extruded product. For years the only way to buy AMS 4640 bar stock form inventory was solid bar not tubing and since many of the applications for AMS4640 (C63000) were for bushings there was a lot of wasted material boring the solid bar into bushings.
One of the leading continuous cast manufactures spent a lot of time and effort showing Boeing that continuous casting and centrifugally casting aluminum bronze was a major cost savings in the manufacture of the bushing in their landing gear and still provided the mechanical properties necessary for a very critical application. They developed the alloy C95510 as a substitute for C63000 (AMS 4640) Boeing has approved it for many applications, and it is now becoming an industry standard as ASTM B 271 C95510, or ASTM B 505 C95510, or AMS 4880. So the next time you see the terms AMS 4640WMM know that the person is probably offering a cast product not an extruded bar.
Courtesy a converstion with Tom Smith
