Just posted this video on Youtube, about milling out a casting mold by using a block of carbon graphite. The carbon graphite is very easy to mill and give a decent finish. I used the 1/8 end mill to get the pocket and V shape bit for letter engraving. The letter is only carved 0.6 deep, I think deeper will give a more clear appearance on the casted letters. We have tryed with Zamak and Pewter, easy material first. Hopefully, I can give it a try on Silver soon.
Here is the youtube link: