Retro fit core drill for motorised z axis, suggestions.

I have a new project and I want to cut some cores out of stone so I'm thinking of getting a, not so expensive bench core drill, and retro fitting the z axis so I can be cutting the cores slowly but efficiently and doing other things at the same time.

I'm thinking a pulley and motor may slip .. unless say I use a toothed car cam wheel type setup ? Direct stepper motor may be a bit to large to produce the torque ? Not sure I'm no expert :)

Example pic

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its basically a very small version of this below which i think is really cool lol :)