Went to France last year, made it to London with half a trad rack in my carry-on. They made me check the baggage because of a suspicious looking nut tool. They didn't make me pay for the extra checked baggage on that flight.
On the way home I carried a set of nuts and cams and put the offending nut tool in my checked baggage. They didn't like the looks of my #11 nut and made me check the bag. That cost me $100 extra.
To avoid future hassles and $ I will always check metal climbing gear on international flights.
