Can't think why it might be a problem (and I used to work in airline security, albeit only for one summer season back in 2004)? It's not like it's much of a weapon. There are much better items freely available if you are planning to hijack the plane. Bottles of duty free booze spring to mind.
I once got pulled up at security at Birmingham, flying to Glasgow after a day out at the NEC motorcycle show. Had bought a set of allen keys which weren't allowed as hand luggage. Had to go back and check them in. Then went back through security and had something to eat at the airside Wetherspoons. The meal was served up with a metal knife and fork. 🙄