Hi, Please I'd like to make this detail into my model (u-boat of revell). The detail consist of a circular line. You can see the detail in this image. What is the method to make this detail. I have the "Dremel machine", but I don´t know what is the accesories that I need. Thanks

Try to find a metal tube that you can sharpen and use to either twist to 'dent' a recessed circle or to push from the back side to make a raised circle.

or

You could use a small slice of cut tube styrene and then sand it down.

Thanks Slodder, but I suppose the problem is the thickness to the plastic model , no? I need to make a lot of pressure over the model, or not. I need to prove this method. Thank you very much for your answer.

One thought - if the plastic is to thick you can thin it from the back side with a rotary tool that will make it easier to work with. You can also carefully experiment with heat - use hot water to the temperature changes aren't too drastic and are easier to control than open flame.

Thanks , good idea. I'm trying to make your method. OK, thanks you.