Definition
A cold-working process in which the surface of a metal part is bombarded with a stream of small, round steel or glass shot. Each impact creates a tiny dimple and leaves the surface layer in compression, which increases the part's resistance to fatigue cracking and stress corrosion.
Plain English
A way of strengthening a metal part by blasting its surface with tiny round pellets. The countless small impacts squeeze the outer layer of metal, making the part less likely to crack from repeated stress.
Context Anchor
Seen in aircraft maintenance and repair instructions for stressed parts such as landing gear parts, springs, shafts, and some propeller or engine parts.
Derivation
Shot' refers to the small spherical pellets used to strike the surface. 'Peening' comes from the word for the rounded end of a hammer (the peen) and the old practice of hammering metal surfaces to harden them. Shot peening is essentially the same idea performed by thousands of tiny hammer blows from flying pellets.
Why Pilots Care
Shot peening extends the fatigue life of critical parts that undergo repeated loading, directly improving safety and reducing the risk of in-flight failure.
Analogy
It is like giving the surface of the metal thousands of tiny, controlled hammer taps so the outer skin is left slightly squeezed and less likely to start a crack.
Intuition Check
Do not read “shot” as a photo or injection here. In shot peening, the “shot” is the stream of tiny pellets used to work the metal surface.
Example Sentence 1
The crankshaft journals were shot peened during overhaul to restore the surface compression and extend fatigue life.
Example Sentence 2
Technicians verified that the engine compressor blades had been properly shot peened during overhaul.