Coring

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mstrlucky74

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I’m told guys doing standard 2-4” core drills through a 6” thick slab get 3-4 cores out of a bit before it’s toast? True?
 
While I know I get more than 10 holes out of a core bit, I add 10% of the cost of a new bit as an expendable for the bid price for a job that requires core holes.
 
don_resqcapt19 said:
While I know I get more than 10 holes out of a core bit, I add 10% of the cost of a new bit as an expendable for the bid price for a job that requires core holes.
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Well field guys are telling me they on get 3-4 cores out of a bit.:huh: I add cost for bit as well.
 
mstrlucky74 said:
Well field guys are telling me they on get 3-4 cores out of a bit.:huh: I add cost for bit as well.
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If you drill the wet core holes correctly you will get many more than 4-6" deep holes. Just don't buy cheap junk core bits. In my experience guys do not use enough water while wet coring.
 
The teeth are steel with diamonds in them, you pump water into the core bit to cool and lube the bit, flushing a slurry of concrete, stone, metal out of the curf cut by the bit. If your men only get 4 holes per, than it is probably dry core or you are coring through lots of rebar.
 
sameguy said:
The teeth are steel with diamonds in them, you pump water into the core bit to cool and lube the bit, flushing a slurry of concrete, stone, metal out of the curf cut by the bit. If your men only get 4 holes per, than it is probably dry core or you are coring through lots of rebar.
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BTW, its a wet core that they are saying 3-4 cores per bit.
 
Wet core 99.12% of the time, dry core when water can not be used.
Unless you are burning through a lot of steel (loading docks, power plants) or cheap bits, your men need proper training; the drill has a clutch and may have a pressure gauge on it so even binding the bit shouldn't kill it. Find out if the teeth are breaking off or grinding down.
 
infinity said:
Either junk bits or not being used correctly.
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Yeh somethings up. Are these Harbor Freight drill bits or something?

The hardest thing I (well, my helper) ever drilled was an 18” thick parking deck with rebar every 3” and we got almost two dozen holes without changing bits. It took a solid two days to drill it and idk how many hundred gallons of water.


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We have great coring subs......I know the exact cost, zero liability.
Why pay electrician wages for 2 or 3 men to core 4" holes?

Guess what happens on the 3rd floor when you wet core 4" holes on the 4th floor, if you don't know what you're doing?
 
Several years ago, I used a rented 6" core bit (like the ones in the pic I posted above) for an exhaust duct to cut through an old (around 100 years) brick wall that was 3 or 4 courses thick. It took maybe 10 minutes, and made a beautiful, perfectly round and smooth hole, and a pile of red dust.
 
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