Definition
A metal casting process in which molten metal is poured into a reusable metal mold under gravity. The mold, typically made of cast iron or steel, is used repeatedly to produce many identical parts with good dimensional accuracy and surface finish. It is distinct from sand casting, which destroys the mold after each pour, and from die casting, which forces metal into the mold under pressure.
Plain English
A way of making metal parts by pouring liquid metal into a strong metal mold that can be used over and over to make the same part many times.
Context Anchor
Seen in aviation maintenance discussions about how engine and aircraft parts are manufactured.
Derivation
‘Permanent’ comes from Latin permanere, ‘to remain to the end.’ In this process the mold is permanent — it stays and is reused — unlike sand molds, which are broken apart after one use. That contrast is the whole reason for the name.
Why Pilots Care
Many engine components a mechanic handles — pistons, cylinder heads, accessory housings — are made by this process. Knowing the casting method helps explain why parts have certain shapes, tolerances, and material properties.
Analogy
It is like using the same metal muffin pan many times instead of making a new disposable shape for each batch.
Intuition Check
“Permanent” does not mean the finished part lasts forever. Here, it means the mold is permanent enough to be reused for many castings.
Example Sentence 1
The cylinder heads on this engine are produced by permanent-mold casting, which gives them a finer grain structure than sand-cast parts.
Example Sentence 2
Technicians inspected the permanent-mold casting for surface defects before installing the new cylinder head.