I have to drill 2 - .3125 holes in 1 inch aluminum round bar. These 2 holes need to be dead center and exactly 90 degrees apart and do NOT intersect.. I have made 2 attempts and the closest i came was a 4 degree error. The drill seems to be drifting.

Any tips or tricks. Should i drill small and try a reamer? Maybe drill with a smaller drill to pilot and then step up to the 5/16?