Also, it helps to drill slowly or the drill bit can wander slightly while moving through the material. Using a short drill bit helps too. If the exit holes are even slightly off centre compared to the entry holes, then getting the blocks to bolt up can be a pain due to the bolts not quite being square to the blocks/floor/support angle/nutplate sandwich.
I ended up using a lathe and a drill stock for mine, I just couldn't quite get it right using a drill press.
Paid up - Dec 2018