I dont know what those sign mean in drafting ?

[wowpilot]

can anybody help me about symbols and signs in drafting ? for example A letter downside of the circle which cut throuh center with line ?

 

[MrCATIA]

If you're asking about the Ø symbol, this is the international drafting symbol for a diameter.

Here's a link that shows a list of various mechanical drafting symbols: http://www.draftingzone.com/shoppingzone/6-1.pdf

If you have a different symbol, please attach a picture of the symbol you're asking about and a picture of the entire drawing to help us provide an exact answer.

 

[MrCATIA]

You might be asking about Datum Target symbols. These symbols define the areas used to establish the datum planes used in GD&T (Geometric Dimension and Tolerance) systems.

Here's an example drawing with Datum symbols (square) and Datum Target symbols (circle): http://images.books24x7.com/bookimages/id_17892/figu36_1.jpg

 

[wowpilot]

Thank you so much for Pdf file which helped me a lot