A shot blasting machine throws steel shot or grit at high speed onto parts to clean off rust, scale, sand and old paint, and to give a rough surface for painting. Airless machines use spinning wheels to throw the shot; air-blast machines use compressed air through a nozzle. The abrasive is collected, cleaned and reused.
Quick facts
- Main types
- Tumble (barrel or belt), hanger, table, roller conveyor, air-blast room
- Abrasives
- Steel shot, steel grit, aluminium oxide, glass beads
- Throwing method
- Turbine wheels (airless) or air nozzles
- Typical result
- Sa 2½ cleanliness for painting, with a set roughness
- Dust
- Needs a dust collector
- Used for
- Castings, forgings, heat-treated parts, structures before painting
Types and what they suit
| Type | Suits |
|---|---|
| Tumble (belt or barrel) | Many small castings, forgings, fasteners |
| Hanger | Medium and large castings, frames, hung on hooks |
| Roller conveyor | Plates, beams, pipes and long fabrications |
| Table | Flat or delicate parts on a turning table |
| Air-blast room | Very large or odd parts, done by hand |
Main parts
- Blast chamber lined with wear plates
- Turbine wheels (or nozzles) that throw the abrasive
- Elevator and separator that collect and clean the abrasive
- Dust collector with filters
- Work handling: tumble belt, hooks, conveyor or table
Good to know
- Steel shot gives a peened, rounded surface; grit gives a sharper profile for paint
- Too large an abrasive can damage thin parts and threads
- Mask threads, bores and machined faces that must not be blasted
- Paint soon after blasting, before new rust forms
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Questions
- What is the difference between shot blasting and sand blasting?
- Shot blasting usually throws steel shot or grit with wheels, and reuses it. Sand blasting traditionally used sand through an air nozzle; silica sand is now avoided for health reasons and replaced with other abrasives.
- What does Sa 2½ mean?
- It is a surface cleanliness grade (ISO 8501-1) meaning very thorough blast cleaning, with only light stains left. It is the usual grade asked for before industrial painting.
- Which shot blasting machine suits small castings?
- A tumble blast machine. Parts tumble on a rubber or steel belt so all faces get blasted in one batch.
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 18 October 2026.