Nottingham timber supplier FW Mason & Sons has been fined £4,000 by magistrates for a breach in health and safety.
The company pleaded guilty to health and safety breaches after a worker was seriously injured when he was dragged into moving machinery.
The employee had climbed over a conveyor to replace a belt when his trousers caught.
Injuries sustained required extensive surgery and he was off work for three months.
The court heard that safety systems had since been upgraded.
District judge John Stobart said a practice had grown up at Masons of replacing belts while the machine was still active.
The company was also ordered to pay costs of £2,490.
