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I'm having some electrical upgraded and I need to drill a 2-1/2" hole through my 8" foundation. The foundation is poured concrete and has small rounded stones inside. This house is almost 100 years old so I'm expecting the concrete and stone to be harder to get through than a newer style straight concrete foundation.

I'll be borrowing a Bosch (Bosch hammer model) 11236VS with an SDS Plus bit that has both hammer and rotary function.

What type of drill bit is ideal for this job?

Is a 2-1/2" x 9-1/2" Diamond Dry Core Bit ideal? Or, would a carbide tipped hole saw do the job? The diamond bit is more expensive, but I'd be willing to spend more if it means get the job done easier.

I won't be hiring a core driller for this job, I'm a DIY and am doing this on my own, so any feedback on doing it myself vs. suggesting hiring someone appreciated.

Any insight around the bit, method of drilling, and what to expect are appreciated.

FreeMan
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CodeVar
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1 Answers1

15

Core drill, preferably wet. Look into rental for the tool.

If doing it with a dry bit, stop often to vacuum the dust out and allow the bit to cool. If you overheat diamond it either turns to charcoal or comes unbrazed from the backing. A wet core drill will flush out the swarf and cool the bit as it goes.

Ecnerwal
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