Patrick Duke, then aged 53, from Rushden, Northamptonshire, became trapped in the machine in March 2012.
He had not been trained in using the equipment, St Albans Crown Court heard.
Amey LG was fined £150,000, Lafarge Aggregates, £175,000 and Ashmac Construction, £30,000. They all admitted health and safety breaches.
Mr Duke was trying to unblock a chip spreading machine on South Way in Hatfield, Hertfordshire, when he slipped.
He was trapped in the equipment for more than two hours and his arm was mangled, the court heard.
After 13 hours of surgery Mr Duke's arm had to be amputated.
Judge Andrew Bright QC was told Mr Duke had never seen a chip spreading machine manual and had not been given proper training on how to deal with the machine.
Ashmac continued to pay Mr Duke's salary after the accident and was handed a lesser fine as it provided labour but had no control of the operation on the site.
The three companies were also ordered to pay £18,000 costs each.
Three firms have been fined after a road worker's arm had to be amputated when it became stuck in a chip spreading machine.