After several weeks he says to the farmer, "What do you do for a screw around here?"

"Oh that's easy." said the farmer, "I use the milking machine, sucks like the best!"

"Oh fuck off!", the guy said, "I can't do that." But that was all the farmer had to offer.

After a few more weeks the guy was getting desperate for a fuck so he thought about what the farmer said.

So he put his dick in the machine and it automatically turned itself on, as it was supposed to do.

The trouble was he couldn't turn the damn thing off.

He screamed for help as the farmer passed on his tractor.

"Don't worry son, he said, "When the buckets full it'll turn itself off."

Thanks to Greg for the great joke.