Where can I have design components drawings with dimensions?

Or I read the question wrong.
Are you looking for drawings to practice from?
Or are you looking to have drawings made of your product?

How about a steam 'engine', for simplicity sake?

http://modelengineeringwebsite.com/Simple_steam_engine_plans.html

https://www.google.com/search?hl=en&tbm=isch&source=hp&biw=1220&bih=939&ei=RwKvWufzAYbtzgKF9L64CA&q=2d+drafting+drawing&oq=2d+drafting&gs_l=img.1.1.0l4j0i30k1j0i5i30k1j0i24k1l4.3196.7690.0.13974.13.13.0.0.0.0.98.964.11.11.0....0...1ac.1.64.img..2.11.962.0...0.9pmUuRemZHo

A dozen other similar search terms will also generate good results.
2d drafting lessons
2d drafting practice

You Can Log On TraceParts.com and you'll find all the components you need with their dimensions.