IMO big mistake to use a hand drill, particularly a pistol handle type. With a D handle drill you can do an okay job if you’re really skilled but you can still end up with egg shaped holes. Not a good thing if you intend to tap threads. You’ll need to work your way up, starting with a pilot hole and drilling the hole slight larger in steps instead of starting with the final size for your tap. The chips won’t come out as a nice continuous string but break off short causing the bit to chatter badly.
Disassembling it and clamping the top to a drill press is no small task and getting it reassembled in proper alignment will be harder but if you want it done right that’s the way to do it. I’m sure that contractor saw wasn’t free so there’s no sense in screwing it up. Do it that way and you can drill the hole, tap it (using the drill press quill to hold the tap handle) and countersink the hole slightly to chamfer the edge without any misalignment. Personally I’d try to find a way to use the existing holes in the saw top.