The World’s BEST Portable Sawmill Value. If you’re looking for the biggest, toughest, best value of all, you’ve found it…The Frontier OS31 is the one for you if your trees, dreams and personal project goals are BIGGER. Hey, we get it. You don’t have to be a full-time pro sawyer to need (or want!) a machine capable of tackling larger logs and heavier jobs. You’re serious and you want bigger equipment to get er’ done. The Frontier OS31 maximizes the bang you get for your sawmilling buck.