No reason why a hand drill can't do this or that a fork would spontaneously explode. But I don't suggest installing anything in that hole that requires any amount of securement, like a rack. Most every mid blade boss I have seen used some sort of braze on to best handle the forces.

The simplest, and likely most common, way is a hole drilled in the outer side of the blade and a bottle cage boss brazed into this. Sometimes with a star shaped reinforcement.

Still having a drilled hole in the blade is the through hole method. The hole is drilled through both the outer and inner side of the blade and a tube, usually unthreaded, is brazed into the blade. This came about with the "over the tire hoopless" low rider racks (Blackburn comes to mind) and a simple long bolt goes through the tube with a common nut securing it all.

A no blade hole method is to use a hourglass shaped seat stay rack boss placed on it's end for the low rider boss. This provides some stand off for the rack, from the blade, and the method I have used a number of times.

In each method the clamping forces are not trying to crush the blade, as would be the case with what I read the OP's idea as being.

Back when brakes were nearly all bolted on calipers some bike companies did a poor job at making a rear brake bridge mounting. Many companies would just through drill the brake bridge and using washers/spacers with a curved side clamp to that bridge tube with no hole reinforcement. Sometimes this worked well, the bridge tube was of sufficient strength to not crush down (which would then let the brake caliper rotate from the brake forces), sometimes less so (Raleigh had a reputation for this issue on their basic bikes). But the result of a rear brake not working or locking up (either end of the range of what we call function) is of less potential than that of a fork blade beer canning.

I strongly suggest not drilling a rack mounting hole that won't also be reinforced somehow and that won't create tube crushing pressures from the hardware. Using U or P clamps is a far safer method. If this isn't what you want then either shift your goals, get a fork with said braze ons already in it or learn how to braze (and paint...) Andy