I have no problems getting metal cutlery on aircraft when flying to the US from a number of nations, including on US carriers.

They're already on many airplanes, at least in F and J classes - and a heck of a lot more than 12.

But I'd chances are good the knives probably won't fly. Send them UPS or FedEx - plus they'll be properly insured this way.

Not sure where you're travelling to/from, but UPS Ground and FedEx Ground services are relatively inexpensive within the USA. It only starts getting expensive if you must send them overseas -- or if you decided to send them UPS Red next day air.

SDF_Traveler