Mix together the flour, baking soda, and sugar. Cut the butter into the flour mixture (rub the butter through your fingers, coating each bit with flour mixture; keep this up until the mixture looks crumbly). Mix in the raisins. Add in the buttermilk-you may need a bit more. Knead the dough a bit. Shape into a round dome on a greased baking sheet. Cut an "x" across the top, then brush with a little milk. Bake at 375 deg for 40-50 minutes.