You will need very little math knowledge as a machinist. A few fractions, some percentages, knowing how many inches are in a foot, feet in a yard, what the area of a circle is, etc.
What you will need much more importantly than that is to follow safety precautions and to have an extremely steady hand. A lathe, a mill, or or a stamping press can easily rip off anything from a few fingers to half your arm. There are many jobs where it's fine to fuck around every once in a while, but machining is not one of them. Quality and safety will be your biggest concerns in your work, so take them seriously.