Members of the International Association of Machinists Lodge 851 went on strike after voting overwhelmingly to reject management's contract proposal, WBBM-AM, Chicago reported.
"Pay increases that were offered were called market-based wage increases, which have no guarantee of any amounts," said Joe Nuske, chairman of the union negotiating committee.
The union said healthcare premiums for a single person would double under the contract proposal.
The company said the strike was unfortunate, but would not disrupt production of hydraulic components, which are made at the plant.
About 800 workers are involved in the strike, WBBM-AM reported.