MIMF

Is it normal to make a small relief on the fingerboard of a violin and i this case how much?

When I press the string to the board on both ends simultaneously, thus making the string a "straightedge", I expect to see approximately the diameter of the string underneath the string itself. Probably there are more sophisticated ways to approach it. The center of that scoop is not in the center of the board, but slightly south. Maybe there is a precise measurement somewhere....

Thanks Chet. No nead for precise measurements. I fully understand your description. When making the relief on the Spanish guitars that I build, I dont meassure, but I know what I want.

The conventional thinking is .03 inches or three quarters of a millimeter under the "G" at the neck stop diminishing progressively to a quarter of a millimeter under the "E" at the neck stop. Personally, I don't think that it is necessary at all. A fingerboard/neck made perfectly straight will always have some natural relief under the tension of the strings, even if undetectable by the naked eye.

I was taught similar to Barry. ("Make it look like this" were the precise instructions, and believe me, it had to look EXACTLY like that). Player preference will sometimes influence, also. My favorite tool for this is the little Lee Valley "Apron" plane, SHARP blade.
JF