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Discussion Starter · #1 ·
Dear DIY experts:

I was drilling 1" diameter hole in 4" thick concrete slab using concrete drill bit and Bosch corded hammer drill with SDS chuck. At some point the drill started vibrating strongly and then the drill bit got jammed - the chuck was spinning but the bit was not. After inspection I concluded that the drill ran into a metal, perhaps rebar. Should I try to temporarily switch to metal drill bit or is there a better method?
The extra details: I was actually using 3/4" concrete drill bit (which I was planning to follow by 1" bit) in pure rotary mode (no hammering) when the problem occurred.

Best Regards
Ivan
 

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Jello Wrangler
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495 Posts
Post tension slabs aren't that common in residential. They would also see that the cable is in an enclosed housing and wouldn't have concrete around the cable itself. It would also look like a cable not solid rod of metal. Seems like they are hitting rebar and not a pre-stressed tendon.
 

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Civil Engineer
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Chitown, I am curious what your basis is to conclude that the OPS likely ran into rebar. The OPS makes no observations about what he ran into, only that he thinks it was metal. He also states the slab was 4 inches thick. I have examined dozens of houses built down south with post tensioned or prestressed slabs, very common in expansive clay country. Not so common in Pennsylvania, as you note, but certainly possible. My experience with normal reinforced 4 inch slabs is that there is typically welded wire fabric reinforcement rather than steel bars. I was simply trying to warn the OPS about the potential for hitting stressed tendons, if you cut them it is an experience you will probably regret.
 

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Jello Wrangler
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495 Posts
Chitown, I am curious what your basis is to conclude that the OPS likely ran into rebar. The OPS makes no observations about what he ran into, only that he thinks it was metal. He also states the slab was 4 inches thick. I have examined dozens of houses built down south with post tensioned or prestressed slabs, very common in expansive clay country. Not so common in Pennsylvania, as you note, but certainly possible. My experience with normal reinforced 4 inch slabs is that there is typically welded wire fabric reinforcement rather than steel bars. I was simply trying to warn the OPS about the potential for hitting stressed tendons, if you cut them it is an experience you will probably regret.
You already listed some reasons. It's only 4" thick, which is a bit on the thin side for a post tension slab (usually greater than 6"). He didn't hit the sheathing, which is larger than a metal cable and not metal itself. His area of the country. So there were a lot of reasons I doubt he's hitting a cable from a post tension system. Oh, and that's another, he said rebar and not cable.

I also think that saying it's "very common" is a bit of a stretch. It's becoming more common, but I wouldn't personally use the term "very common".

As for using the term rebar, I was just mirroring what he said, instead of saying it was wire from a mesh, it's what he referred to it as and I saw no harm in continuing the vernacular.

I guess I would have also expected more help when cautioning someone concerning something that they obviously don't know much about. You told him to be careful and make sure, but didn't follow up with how to be careful and how to make sure.
 
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