Stable-Cast® is Palmer Foundry’s own proprietary series of heat treated aluminum casting alloys that provide dimensionally stable aluminum casting without sacrificing machining properties. With the Stable-Cast® series, machining operations can be high speed and distortion free, without interrupting the machining process for intermediate stress relieving. Aluminum castings made with the Stable-Cast® processes are very cost effective for high precision applications.

Instrument castings usually require superior dimensional stability and excellent machining properties combined with good soundness and cosmetic appearance. Machining characteristics and stability are primarily a function of casting alloy and associated heat treatment, while soundness and cosmetics are determined mainly by good casting design combined with high quality foundry practices and attention to detail.

Compared to the more widely known 356-T6 and 356-T51 alloys, the Stable-Cast® series of aluminum casting alloys from Palmer Foundry provide extraordinary stability without sacrificing machining properties. The table below summarizes the relative performance of these materials compared to the 356 series:


Stable-Cast® 3 Stable-Cast® 6 356-T6 356-T51
Ultimate Tensile 30,000 34,000 33,000 25,000
Yield Strength 26,000 24,000 24,000 17,000
% Elongation 1% 3.5% 3% 2%
Brinell Hardness 85 75 75 60
Machinability 1 1 2 4
Stability Rating 1 1 4 1
Material Cost 1 3 3 2
Castability 2 1 1 1

Note: Relative ratings (1=excellent, 2=good, 3=fair, 4=poor)

From Table 1 it is easily recognized that 356-T6 suffers from poor dimensional stability while 356-T51 has poor machining characteristics. These drawbacks limit design flexibility and performance while increasing costs. In comparison, Stable-Cast® 3 provides the best overall choice for most high precision casting applications. We recommend Stable-Cast® 3 for most instrument applications. If improved castability is essential due to the complexity of the configuration, then Stable-Cast® 6 is normally used. If the application requires the unique combination of high stability and ductility, then HyDuct5 is recommended.

If you require castings with excellent stability and machining, the Stable-Cast® alloys from Palmer Foundry can meet and exceed your expectations. Call us today at 413-283-2976.