Quint GD&T
The popular YouTube channel Quint BUILDs originally made in-depth engineering videos on something called GD&T. It's a standard published by ASME (American Society of Mechanical Engineers) used to define fits of manufactured parts. Quint has a senior level certification in GD&T and originally made videos to help others understand it. They're all here FREE for anyone looking for help on that topic. You may still see new content here but most of Quint's effort is currently directed to Quint BUILDs. That content is more appealing to a general audience which is why it gets MILLIONS of views rather than thousands.
If you gained something from these videos and want to give back, you can make a one time contribution on PayPal: [email protected] or consider becoming a patron of Quint BUILDs.
There's also one piece of pay-only content, a study guide Quint created based on the free videos.
Find more on that here: https://youtu.be/WLQJ8q_zpA0
Thanks and good luck learning GD&T!