Here's how I drill for lock bolts:
Find the positions that you want the bolts to go on on the lock side. Carefully measure and mark the position for the front lock bolt especially closely. When satisfied with positioning, lay the stock on the sideplate side on the drill press, and drill through with the tap size (for 8-32, that's number 29). The drilled holes will be perpendicular now to the sideplate side, which is what you want (the screw heads draw down flat). Depending upon exactly where the screw hole is, and where the breechplug tang is, you may or may not have to drill through the plug. If so, do it now. Make sure that it is TIGHTLY clamped down in place. Now, put the lock in place, clamp it in, and with a hand drill, go through the holes from the sideplate side and drill through the lockplate. Remove the lockplate, and put the stock (with barrel, if you drilled through the breechplug) back on the drillpress, sideplate side down, and redrill through the holes with your through size drill (for 8-32, through size is supposedly 19, but that will be too small, and it will end up needing to be 18). Then, put the lock back in place, and tap through the stock into the lockplate (no oil...it will soak into the stock. For a couple of holes like this, it isn't really necessary if you have a good tap). This way, the threads will be properly aligned with the holes. And there you have it.