Shot peening blasts a part with small round steel, glass or ceramic shot at a controlled speed. Each hit leaves a tiny dent that stretches the surface, leaving the skin in compression. That compressive layer makes cracks much harder to start, so springs, gears, shafts and welded parts last far longer under repeated loads. It differs from shot blasting, which cleans rather than strengthens.
Quick facts
- Purpose
- Longer fatigue life, resistance to stress corrosion
- Shot
- Cast steel, cut wire, glass beads, ceramic
- Control
- Almen intensity and coverage (often 100–200%)
- Depth affected
- About 0.1–0.5 mm (0.0039–0.0197 inch)
- Typical parts
- Springs, gears, shafts, crankshafts, welded joints
- Standard
- Often SAE AMS 2430/2432 or a customer spec
Shot peening or shot blasting?
| Shot peening | Shot blasting | |
|---|---|---|
| Aim | Strengthen the surface | Clean the surface |
| Media | Round, graded shot | Grit or shot |
| Control | Intensity and coverage measured | Visual cleanliness |
| Typical parts | Springs, gears | Castings, fabrications before painting |
What to tell the peener
- Part drawing and the areas to peen or mask
- Shot type and size, Almen intensity and coverage required
- Material and hardness
- Certificate or Almen strip records needed
- Quantity
Need shot peening done?
Post your requirement free. Workshops that take your kind of work see it and get in touch. You only talk to the ones that fit.
Get startedRelated
Related job work
Questions
- Why does shot peening increase fatigue life?
- It leaves the surface in compression, which pushes against the tension that opens fatigue cracks.
- What is Almen intensity?
- A measure of peening strength: a thin test strip is peened and the arc it bends into is measured.
- Can a shot blasting machine peen?
- Only if it can control and measure shot size, speed, intensity and coverage. Ordinary blasting is not peening.
The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 23 October 2026.