Well I'm a little late to this party but I tapped 4 wholes in 1/2 plate of cast iron last week and I dry tapped them.
Only difference was mine were through wholes.
Paul
Paul,
It seems the majority agrees dry for cast iron. I will go with the crowd.
I hope to finish the project tomorrow and I'm going to paint it with the black hammer finish you used on the camel back drill restore if the weather permits. I'll post some pictures.
Benny