This can create challenges for manufacturers who may not easily understand the drawings.
However, not all engineers are comprehensively trained to create clear drawings. Most rapid prototyping customers upload design files and drawings for a better understanding of requirements.
This will allow you to communicate the intent of your design for CNC machined parts. Understanding the basics of engineering drawing is a great first step.
This is even truer for engineers and machinists. Drawings and pictures are among the best means of communicating one’s ideas and views.