Workers at Optare, a Leeds-based supplier to bus and coach companies, struck for 24 hours on Monday of this week.
Talks on the day broke down and workers plan further strikes on Monday and Friday of next week.
The action followed a successful walkout on Tuesday of last week. The solid action by 180 Unite union members is against attempts to force them to take their leave in the middle of August.
For months there have been petty attacks on terms and conditions including bans on radios and talking in groups.
Reballots have opened the way to bigger struggle