Definition
A reusable metal mold used to cast metal parts. Molten metal is poured into the mold cavity, allowed to solidify, and the part is removed. The mold is then used again to produce additional identical parts.
Plain English
A metal mold that is used over and over to make many copies of the same cast metal part, instead of being broken apart after each pour.
Context Anchor
Seen in aircraft maintenance and materials discussions about how metal aircraft parts are manufactured.
Derivation
Permanent comes from the Latin permanere, meaning to remain or stay. Mold comes from the Latin modulus, meaning a small measure or pattern. Together the term describes a pattern that stays — a casting form that lasts for many uses, unlike sand molds that are destroyed after a single pour.
Why Pilots Care
Many engine and airframe components are produced by permanent mold casting. Knowing the term helps a pilot or technician understand part specifications, repair limits, and why some cast parts cannot be welded or reworked the same way as forged parts.
Analogy
It is like using a metal muffin pan instead of a paper cup. The pan shapes the material and can be used again for the next batch.
Intuition Check
Permanent does not mean the mold lasts forever. Here it means the mold is reusable and is not destroyed each time a part is cast.
Example Sentence 1
The engine's aluminum cylinder heads were produced using a permanent mold to ensure consistent dimensions across the production run.
Example Sentence 2
Permanent mold castings provided the smooth finish required for the propeller hub components.