Gene, As a scroll saw instructor at Woodcraft in Ventura CA., the first thing I explain to my students is that a blade will not cut at a perfect 90? to the front face. As Chachi explained, most blades have a burr on the right side from the manufacturing process. this burr causes the "Drift" that you are experiencing. You must learn to anticipate for this drift. Once you accept this, It will become second nature to anticipate for the drift.