threshing machine

David Bright had promised to give Leandro until four, and that was a promise he had intended to keep –because it was honorable, of course, but also because he was not sure this was anything he wanted to stick his hand into. It might turn out to be a threshing machine instead of a news story.
Source: The Tommyknockers by Stephen King

What does threshing machine mean in this context of journalism lingo?
Thank you

A threshing machine separates grain from plants – the operative word here being "separates."

"... he was not sure this was anything he wanted to stick his hand into. It might turn out to be a threshing machine instead of a news story."

My impression, since he used the bold expression, is that he might get his hand separated from his arm, rather than getting a news story. In other words, getting involved could have personal consequences for him, perhaps serious ones.