A man gestured at train staff with a screwdriver after a food trolley accidentally bumped his seat.
The man is reported to have become "verbally aggressive" during the incident on a service between Cardiff and Bridgend on August 3.
British Transport Police are investigating and have issued a picture of a man they would like to speak to in connection with the incident.
The force said the man "pulled out a screwdriver" and gestured at staff members after the trolley bumped his seat at around 2.50pm.
Another screwdriver was seen tucked into his waistband.
The man continued to "verbally abuse" staff until he left the train at Bridgend station.
How police deal with a report of crime:
Anyone who knows the man pictured is asked to contact BTP by texting 61016 or by calling 0800 40 50 40 and quoting reference 376 of 03/08/19.
You can also contact Crimestoppers anonymously on 0800 555 111.
