What is the importance of GD&T?
My teachers and everyone from industry always say that GD&T is the most important, but i don't know why also if it is so important to dimension accurately in Mechanical Design than what about Industrial Design. Do they also have GD&T etc?
One thing it is used for is in manufacturing. It gives definitive reference points for machine/material setup. Industrial Design is not as strict on engineering as Mechanical Engineering studies are, so it is usually not taught. Yes, dimensioning and tolerances are important, but it comes down to the fact that Design is "design", and Engineering is "engineering".
I learned GD&T in college and have hardly touched it sense, there is the occasional need to use it, but not very often for me. Usually typical tolerances work just fine. I have heard around the office that alot of machine shops see GD&T and automatically boost their prices, and then just try to make it the best they can.
When dealing with very small tolerances, +/- .002", it becomes ever more important to use GD&T. If you have a cylinder that need to be "cylindrical" within say .0003" you learn to use it very quickly. Otherwise, you'll have a big mess on your hands. We use it often when we need two or more parts to line up just perfect.
GDT or geometric dimensions and tolerancing works in some sense like normal tolerancing, where measurements have limits how much they deviate from the given number. GDTs difference is where it refers to the shape (usually a line, circle, surface or point) or the relation between two shapes (often perpendicularity of two lines, the concentrity of two circles, etc.) This can become important in the manufacture and quality control of high precision items that need to very exact to function properly.