If you are into prototyping that requires to work with plastics, metals and other materials, so you can materialize a concept or a prototype, these videos will be of a great help.
These videos are done by Dan Gelbart, an interesting person with an interesting background. He covers quite a lot of concepts in many areas with not much long talking and going to the point, which it is very appreciated !!!
You should take a look on his YouTube Channel, here you have the link to the first video, after you will have to search on his video list for the next videos.