Cyril Thornhill, 67, of Plymouth Road, Barry was found guilty of theft after taking a 1.5-tonne Kubota digger belonging to Miles Hire.
The theft took place in Cardiff on January 31, 2023, Newport Crown Court was told.
Thornhill denied the charge during his trial.
He is due to return to the same court on July 28 for sentencing.
Judge Daniel Williams ordered that a pre-sentence report be prepared with “all options” requested for consideration.
Thornhill was released on conditional bail.
The case was prosecuted by Harriet Ealden with the defendant represented by Zoe Laugharne.
