So you know where your tap will be headed, and more importantly, how the swarf will have to exit, here is an inside view.
Nice touch that relief in the land so that the last drop of oil can drain, but it makes washing the swarf out rather tricky.

 

As you see, there are no nooks or crannies for swarf to fall into so long as you tap the hole "the right
way up",  but when you swill the crankcase out,  the swarf will have to be washed out through the narrow
relief gap.  Shouldn't be too much if you use grease, but any larger pieces that are not held by the grease
can form a log-jam at the relief gap and hold back other pieces.

The idea of spinning an Allen key would be limited by the land.
Seven rotations of tap needed.
Good luck.
 

Bernard   (NZ)
Bigzoner #096, English Chapter
" Keep brotherhood till die "