Good morning @wsylvia123 .. curious as to how your son drilled the hole in your cup.. could you ask him what type of drill bit he used and what material the cup is.. I have broken several trying to do this .. thankfully they were not old. 😓
@quinnedy I have drilled some too. We use a 5/8 inch Milwaukee diamond bit from Home depot.They are hollow in the center. We have done probably 10-15 with the same bit but they have a limited life so I bought a set on Amazon of 6 or so for a lot less. Haven’t tried them yet. Have never broken one yet, knock on wood. We start at a 30-45 degree angle til u get a curved groove and then move to perpendicular. Also always keep water on it. It heats up and it will extend your bit life.