Blueprints are less and less necessary these days. With machine technologies on the market now, most of them will take your 3D files. But if you must, here is an example of a blueprint ready for manufacture.
Even when blueprint is not necessary, tolerance calculation is important. In this example Bend radius are hard to reproduce perfectly at low cost.
What is tolerance?
Tolerance is more money for you. The more flexible you are on tolerance, the less you’re part will be costly to manufacture. As precise as machine can be these days, Being precise to a 1/32 of an inch can be costly. A tolerance is a dimensions, properties, or conditions that may vary within certain practical limits without significantly affecting functioning of equipment or a process. Tolerances are specified to allow reasonable leeway for imperfections and inherent variability without compromising performance.