I too ruined a cable, but it took a while for the perms kink to start messing up.
Drilling a kettle: put a piece of masking or painters tape over the spot. Use a sharp pilot bit first. Then a step bit. Hole saw will work, but it's easier to work up from a smaller hole to what you want in my experience. Hole saw is all or nothing. Use a silicone grommet and you won't have to worry about high heat.
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