The 33-year-old plant operator at Coleman and Company’s site in Meriden, Warwickshire, was hurt when his right arm was drawn in between the rollers and conveyor belt.
The worker suffered fractures to his right arm along with wrist injuries and bruising.
He later needed several skin grafts in hospital and has yet to return to work.
Solihull Magistrates’ Court heard that without the swift reaction of his colleagues, who ran to his aid to stop the machine, the injured worker could have lost his life.
The incident in November 2012, at the company’s site in Cornetts End Lane, was investigated by the HSE which prosecuted Coleman and Company for two separate breaches of safety legislation.
HSE found the incident could have been prevented had the company noticed that the machine’s fixed guards had been either removed or lost, and had taken steps to replace them.
Coleman and Company of Great Barr, Birmingham, pleaded guilty to safety breaches and was fined £3,500 and ordered to pay £1,114 in costs.
Speaking after the hearing, HSE inspector Karl Raw said: “This was an avoidable incident involving a dangerous piece of equipment which is designed to crush concrete.
“As such, the consequences of a person coming into contact with moving parts of the machine can be severe.
“The worker involved was very fortunate not to have suffered even more serious injuries.
“Coleman and Company exposed workers to serious risk by failing to ensure that the workers were protected from dangerous moving parts of the machine by suitable guarding mechanisms.
“In addition, the company should have had a system of monitoring in place to identify if guards were missing, defective or inadequate.”