ok so i found a good piece of iron to use for my knife and have already made it to where i can at least cut a tomato and a pepper but when i washed it off and i was being stupid and forgot that it cant get water on it or it will rust so how do i get it to not rust when i wash it off or cut a tomato.

The acid in the tomato is part of the problem.

Wash the knife with soap and water (sanitation). Rise the blade in clear water and immediately dry the knife, followed by a coating of something, such as food grade oil, to keep air (oxygen) from getting to the metal.

ok i'll try this so do i just dip it in the oil

 

The knife makers will suggest their favorite methods and coatings when they see the question.

if i use vegstible oil

Kinda funny as stainless kitchen knives are about 100 years old and plain high carbon steel knives are 1000 years old.

Can you ask a grandmother or a great grandmother---they don't even have to be yours!----how they treated their kitchen knives?

The big thing is to not let them sit wet. I wash and then dry and then put away.  They will patinate; but that is a feature of the old plain carbon steel knives.

I do exactly what Glenn and Thomas said, and it works just fine. Every week, roughly, I wipe them down with a light coating of vegetable oil and they stay in great shape. You could also use canola oil, or olive oil, or peanut oil, etc. Any type of oil that you don't mind touching your food (read as DONT USE MOTOR OIL!)