Place both types of flour in a large mixing bowl and stir to mix well. Make a well in the center of the flour and add the water a little at a time, stirring with your hands until a dough is formed. You may need more or less water, depending on the humidity in your kitchen.
Place the dough on a floured work surface and knead it like bread for 8 to 10 minutes, until smooth and elastic. Cover and let stand for 10 minutes at room temperature.
Roll the dough into long dowels, about 3/4 inch thick. Cut into flat disks about 1/4 inch to 1/2 inch thick. With the palm of one hand, roll one disk out to form a 6 to 8-inch length piece of spaghetti. Set aside and cover with plenty of semolina while continuing with rest of dough.
Recipe courtesy of Mario Batali, 2001