A said, scaling just multiplies the vertices with a scalar. And translation without any rotations being used is just an addition. So if you have two vertices, like (-10,0,0) and (10,0,0) and scale them by 2, you'll get (-20,0,0) and (20,0,0). Translate them by (100,0,0) and you end up with (80,0,0) and (120,0,0) with your virtual center at (100,0,0)...and i guess that is what you expect. However, if your object's center isn't (0,0,0) (which it obviously isn't), then you'll get different results...for example with (0,0,0) and (20,0,0), you'll end up (doing the operations like above) at (100,0,0) and (140,0,0) and your virtual center is at (120,0,0)...and any subsequent scale won't change that vertex at (100,0,0), so it looks like as if the mesh extends to the left only.