Simply, the numbers are different “temper” process on 6061 alloy. – This explains the different T temper processes…. Once a…
The method that is use in most cases is 2 foot short span. I will make the assumption that the 6061T651 Aluminum plate has been purchased to “Type 200® wrought tooling plate or Precision Plate®” specification. If not, standard Aluminum Association tolerance of .100” for thickness of 0.250”–0.624” and .075” for thickness of 0.625”-8.000” would apply (Table 7.18*). A certified 24” straight edge is used in conjunction with certified taper gage or feeler gages and a relatively flat inspection surface.
6061-T651 aluminum is the main alloy of 6061 aluminum alloy. It is a high quality aluminum alloy product produced by heat treatment pre-stretching process. Its strength can not be compared with 2XXX system or 7XXX system, but its magnesium and silicon alloy have many characteristics. Good processing performance, excellent welding characteristics and electroplating, good corrosion resistance, high toughness, no deformation after processing, dense material without defects, easy to polish, easy to color film, excellent oxidation and other excellent features. So widely used in decoration, packaging, construction, transportation, electronics, aviation, aerospace, weapons and other industries.