Standard or Precision--Tolerances Change the Rules

摘要

Die makers and extruders have, from time to time, all conceded to a customer that one-half standard tolerances were possible to achieve on certain shapes but extremely difficult on others. The challenges involved in meeting such tight tolerances meant that they were provided only when specifically asked for. However, the situation exists today where precision tolerances are quickly becoming the new market standard," and extruders and die makers alike should be aware of this change. As of the latest version of Aluminum Standards and Data published by The Aluminum Association in 2006, a new category appeared in the Cross-Sectional Dimension Tolerances Table 11.2. The table now includes not only "Standard Tolerances," but a second category of tolerances, called "Precision Tolerances" (Figure 1). Precision tolerances are approximately 60 percent of the previous standard. Therefore, they are 40 percent less (tighter) than the standard tolerances.