The main difference between sandblasting and shot blasting machines lies in the material used for blasting and the purpose they serve.

Sandblasting machines: 

- Sandblasting machines use sand or other abrasive materials such as garnet or aluminum oxide to propel at high speeds onto the surface being treated. 

- These machines are commonly used for surface preparation, paint and rust removal, and cleaning of various materials such as metal, concrete, glass, and wood. 

- Sandblasting machines are effective for removing old coatings, corrosion, and contaminants from surfaces.

Shot blasting machines: 

- Shot blasting machines use metallic shots, such as steel or iron shots, to propel at high speeds onto the surface being treated. 

- These machines are primarily used for surface preparation, descaling, and deburring of metal surfaces. 

- Shot blasting machines are commonly used in industries such as automotive, aerospace, construction, and foundries. 

- They are effective for removing rust, scale, weld splatter, and other surface imperfections.

In summary, sandblasting machines are used for general surface cleaning and preparation, while shot blasting machines are specifically designed for metal surface treatment and preparation.