Having tried something similar before

And on viewing your fabrication equipment (viz. a pair of mole grips and a cordless electric drill), I can confidently predict you will fail hard in the attempt and land up with an eccentric hole that veers out of the side of your bolt.

I tried drilling down the centre of a bolt myself while trying to make a re-useable threaded bit on the end of a Jawa front brake cable (so I could take a homemade cable all the way through and put a pear nipple on the end). I concluded that it canot be done without either (ideally) a lathe or a very carefully set up pillar drill with a properly level base, a very strong clamp and an engineers try-square.

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