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-   -   Broken bolt emerging from cement (http://www.diychatroom.com/f105/broken-bolt-emerging-cement-181191/)

Mallethead 06-03-2013 12:48 PM

Broken bolt emerging from cement
 
Hello,

I do a lot of work of my own around the house. This past week-end I got a new diving board for the kids and replaced the old one. All was fine until I accidentally broke the bolt that holds the spring plate against the concrete deck.

The broken bolt is approximately 3/8". The threads were exposed above the concrete about 3 inches and I was attempting to remove the nut that holds a thick steel plate in place by threading the bolt downward onto the plate. It was badly rusted and although I was very careful I was not surprised when it broke.

My question is: what is the proper course to take now?

I am thinking that I can use some kind of drill bit to core out the remaining buried bolt. Then, put in a replacement bolt using QuikCrete Anchoring Epoxy. The only thing to be careful of is that the steel plate has a round hole and the bolt comes up from the cement and through the plate so I cannot really increase the size of the bolt or it will not pass through the plate.

If this makes sense I do not know what kind of drill bit to use to core (remove, destroy) the existing bolt.

Any suggestions are appreciated.

Regards,
Mallethead

Willie T 06-03-2013 12:54 PM

Start "dead-center" of the bolt with a tiny bit. Drill it as far as possible, then switch to a little larger diameter bit. Keep doing this. It may take five or six bit size changes, but this will actually be easiest.

It will help to use oil.

Once the bolt is out use a "red-head" anchor for the bolt size you need for the plate clearance.

This ends up being about an hour and a half job.

Mallethead 06-03-2013 01:06 PM

Willie, thanks.

Is a special type of drill bit required? The bolt has been in the ground for 25 or so years and I expect it's hardened over the years. Not really sure.

Jerry

Canarywood1 06-03-2013 01:13 PM

Quote:

Originally Posted by Mallethead (Post 1194253)
Willie, thanks.

Is a special type of drill bit required? The bolt has been in the ground for 25 or so years and I expect it's hardened over the years. Not really sure.

Jerry


High speed steel.

Willie T 06-03-2013 01:42 PM

And, BTW, "High Speed" does not imply that you rev it up to a high speed. :no: That is referring to the type of twist configuration built into the bit. All metals should be drilled pretty slowly, with steady pressure on the bit to keep the cutting edges biting all the time, constantly curling out a spiral of steel shavings. And use cutting oil.

Watch this. You'll be doing the same thing, but with increasingly larger bits throughout the cut. http://www.youtube.com/watch?v=D4q8UhbpaG0

joecaption 06-03-2013 02:23 PM

Grind or file what's left of the bolt so it's flat on top.
Use a prick punch to make a mark in the center of the bolt.
I'd be using at least a titanium nitride coated drill or colbolt.
A high speed steel drill bit may just get the bolt hot and work harden it.
Use cutting oil and go slow.

Canarywood1 06-03-2013 03:31 PM

You can also try renting a concrete core drill if the previous answers don't appeal to you.

Mallethead 06-03-2013 03:37 PM

A sincere thank you to all who answered this question. I have several ideas and some direction now. Great to hear your suggestions.

Regards, Mallethead


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