hope you have a smelting furnace and know how to sand cast.
If you do not know what way scraping is you will when it is completed.
But Dan says it is easy so it must be right?
in the end you wind up with a machine that is not as accurate as the cheapest from horrible fright ... chatters on anything softer then butter.. if anything breaks you basicly have to recast and machine that part as none are available for it.
Now if you want to build one just to learn more about machining and casting this is the way to go but after you add up all the hours and everything else needed and the scrap to make it how much are you really going to save?
All this is only possible if you live out in the country or own your home as having a foundry would be frowned on in a complex
Live life as its your last day... it just may be
Learn to do it right or how to fix it later, quicker to do it right the first time.