How Plaster Cutter Works?

A plaster cast cutter, well known as a cast saw or Orthopedic Cast cutter. It is a specialized medical tool used to safely remove plaster or fiberglass casts from patients fractured limbs without damaging the underlying skin. It is popular used in hospitals and clinics to remove casts after a fracture has healed.

For a regular circular saw, which rotates completely and can dangerously cut the skin.But plaster saw works in different way, it uses a vibrating blade.It is safe.
 

 Its working principle is as follows: A sharp , small-toothed blade vibrates rapidly back and forth at a very small angle ,typically 3-5 degrees. It vibrates at a high speed, it can over 12,500 times per minute. This creates a sawing action, but without full rotation.

Hard materials like plaster or fiberglass cannot bend. The vibrating blade grinds away very small  fragments, creating dust, and effectively cuts through the material.
Soft skin will bend and move with the small movements of the blade. This dissipates the energy—there isn't enough shearing force to cut the skin. Usually, people only felt a vibration or slight tingling sensation..

Analogy: Try scratching or cutting a piece of paper held in mid-air—it will only bend. But on a hard table, it's easily torn. Our skin is like the paper held in mid-air, and the cast is like the hard table.

it is very safe, under the correctly usage. Technicians often demonstrate this by touching the running blade to their own hand.
It will meet some rare risks, applying too much pressure  or for too long may cause minor abrasions on bony prominences, or (due to fiberglass friction) thermal burns.
Best practice: Cut in short bursts, allow the tool to cool, and suction away the dust.