In this script on Technical drawing describes how to bolts and threaded correctly.
The correct representation of threads in technical drawings (whether it is an internal or Außengewinden act) is to DIN ISO 6410-1. The presentation is simplified, since it obviously makes no sense to any thread course in the drawing represent.
For external threads (eg screws), the outer thread and the thread limit with a broad Vollinie drawn. The end of the thread as Conical dome with 45 ° phase-out. The thread core line (ie the inner line) is characterized as narrow Vollinie. In the frontal view draw the line threaded core as a 3/4-Kreis (with a narrow Vollinie).
The figure below shows an example for the external representation of a thread as it is technical drawing.
For the presentation of the Technical Drawing internal distinguish between one of the display in normal (uncut) condition and in an intersection. In the uncut state is in side view the thread core hole, the thread completion of the line and threaded outer diameter as small stroke line.
In the event of a cut is the thread core hole and tapped the conclusion line with a broad Vollinie drawn. Outside diameter of the thread is in contrast a narrow Volllinie executed.
In the top view it behaves well, with the only difference is that outer diameter of the thread as 3/4-Kreis (with a narrow Vollinie) will be drawn.
An example of the internal representation of the technical drawing you see in the picture above.