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Permanent Mold Casting

Permanent Mold Casting is often referred to as Gravity Die Casting.  It is a similar process to Die Casting except that increased pressure is not used to fill the cavity.  Using gravity as the only force behind the molten aluminum allows a more natural mold fill of the casting.  The molds are machined from cast iron, which helps the aluminum to solidify more rapidly, thus increasing production times and material density.  Usually reserved for quantities of 5000 pieces per year or more, here at Marlborough Foundry we employ this process whenever it makes engineering or financial sense.   Our goal is to supply the very best casting that exceeds the requirements and that can be affordably produced.


  • Basic Linear Tolerance up through 1 in. (25mm): +/- .015in (.38mm)
  • Additional tolerance for each inch greater than 1 in. (150mm): +/-.002 in. (.05mm)
  • Machining Allowance: .125 in. (3mm) with a .060 in. (1.5mm) minimum
  • Draft angle: 2 degrees.
  • Surface Finish: 150 to 300 RMS.
  • Wall Thickness: .100 in. (2.5mm) minimum