How do you mean yours is knackered?

will it not push in? they get clogged with alot of dirt, well mine did and i thought it was worn and wouldn't catch on. but i sprayed WD40 in it and left it 20 mins then spent another 20 pressing it in and out like a special needs case and got it working like new again.

It Might help and you get to keep your lockset with only one key