A Coffs Harbour manufacturer has been fined $250,000 after a work experience student's hand was crushed in machinery.

The 17-year-old student was undertaking work experience at Thermal Electric Elements in Toormina in August 2014.

He had been removing metal strips from a brake press when he accidentally activated the machine's knife.

The tips of two of his fingers were crushed and had to be amputated.

An investigation by SafeWork New South Wales found the company had failed to provide proper guarding on the machine by changing its settings, so it did not automatically shut down when objects got too close to it.

The report also found a general lack of instruction, training, information and supervision of the student.

In handing down the fine, SafeWork executive director Peter Dunphy said the judgement had taken into account the permanence of the injuries and the fact the teenager's future employment prospects had been affected.

"This has left a young worker with lifelong injuries," he said.

"Setting the machine so that it operated while body parts were near the knife was an action that created significant health and safety risks to workers.

"This court decision sends a strong message to the business community, of the need to protect young and vulnerable workers so that tragic incidents like this do not occur.

"Safety guarding is a very simple way to protect workers from being seriously injured or killed."