Hi Rick,
here it is, after a hard day at work, I needed to change my mind so I passed the evening in the shop and here it is :
http://www.labellenote.fr/file/Metal...ilieu_pile.JPG
http://www.labellenote.fr/file/Metal...ilieu_face.JPG
http://www.labellenote.fr/file/Metal...140_mesure.JPG
http://www.labellenote.fr/file/Metal...ce_mediane.JPG
Thinking about it, I simplified the scribe by leaving only a 1 mm hole, just enough to pass the tip of a pencil.
Works great !
Thanks for the idea !
I have some step by step pictures, I will put an article on my site one day or the other, I will make reference to your original idea , Rick, of course !
Cheers,
Christophe