Dogtrousers
Kilometre nibbler
And the core will never cool. So is an unlimited source of clean energy.
The sun will blow up earth before the core has time to cool.
It is rather frustrating that there are all these resources and energy down there. All we have to do is dig a hole. It doesn't even have to be all that deep, a couple of hundred kilometres should do it. That's only as far as London to Birmingham (ish)
I mean, how hard can it be?