Anytime you run a tap into the car it should have heavy grease on the threads... and go in and back out in small increments cleaning the threads each time it is backed out...
But this is also one of the better places to leave metal shavings in... if one has to do that... first, you can flush from the top just by pouring oil in... and second, this is on the outside of the screen for the oil pickup...and the oil filter...
So , all in all, a pretty safe operation if you understand the physics of heavy grease.... this is used when reaming the glow plug holes also.....a pretty standard machining trick...