GMB union members at Mothersill Engineering in Cumbria walked out for the second Friday in a row last week as part of their fight for better pay.
The workers voted unanimously to launch a series of strikes.
The workers—based at a factory at Lillyhall, near Workington—are demanding that bosses backdate their 2.5 percent pay rise, which was offered in July, to January.
Bosses have refused to do this, even though it is the usual date for wage rises at the firm, and they have refused to speak to the Acas conciliation service.
The union had deferred pay talks until June because of worries over the economy. But Kevin Young, the GMB organiser, said, “We were left with no alternative but to strike. We will be on strike for the next nine Fridays and that could be ramped up to more days.”