Ask HN: News aggregrator sites for mechanical engineers

So HN has been invaluable as a source of news, blogs, guides and general tips relevant to our industry.

I have a mechanical engineering colleague and was wondering if there are similar sites like HN for mechanical engineering related news. I know HN itself is a pretty rare and high quality site, but you never know.

I am aware of the reddit groups /r/engineering and /r/MechanicalEngineering, but is there any other similar sites?