Terrence McCann, 46, was found with the home-made knife while imprisoned at HMP Stoke Heath in June last year.
He denied possession of an offensive weapon but was found guilty by a jury following his trial at Shrewsbury Crown Court yesterday.
Following the verdict, McCann, of Liverpool, started singing 'Que sera, sera. Whatever will be, will be'.
During the trial, the court heard McCann was searched after he punched a prison officer, less than an hour after he arrived at Stoke Heath.
He had been transferred from HMP Liverpool earlier that day.
Several officers who worked at Stoke Heath gave evidence at the trial, including Joe Dunworth who said he became aware of McCann when he pushed into a meal queue at about 4.40pm on June 18, 2018.
Mr Dunworth said that he and his colleague Peter Doherty confronted McCann, who became abusive and started making derogatory anti-Scottish remarks about Mr Doherty.
McCann went into a cell in the prison's G wing and the officers followed him.
He swung a punch at Mr Doherty's arm and a struggle began, said Mr Dunworth.
McCann was restrained by Mr Dunworth, Mr Doherty and a third officer, and eventually calmed down.
Shortly after the confrontation he was searched and the improvised metal weapon found.
McCann is expected to be sentenced at Shrewsbury Crown Court this morning.