Wednesday, June 12, 2013

Removing Dynabolt Sleeve Anchors

While putting up the frame for my sister's chicken coop I made a slight mistake.  My attention wandered and I managed to fit a Dynabolt, or sleeve anchor as they're sometimes called, in the wrong place.  The bolt was being used to anchor a 35 mm thick pine frame to a concrete slab and once in place they're notoriously difficult to remove, so I thought I'd document how to go about doing it.  I'll refer to the bolts as Dynabolts from here on.  Although it's a brand name, it tends to be what all bolts like this are called in Australia.

First remove the nut from the bolt and tap it into the hole with a hammer until it bottoms out.  The key to removing a bolt like this is being able to get to the sleeve that surrounds the bolt.  To do this I had to remove the nuts from the surrounding anchors and lift the frame slightly.

Frame with Hole
Top Sleeve in the Frame
Dynabolt/Sleeve Anchor
Dynabolt and Lower Sleeve

To understand how to remove Dynabolts it helps to understand how they work.  In the image below you can see the 4 parts of the bolt I was using.  The nut, bolt, upper and lower sleeves.  Before installation the bolt needs to be assembled by placing the lower and upper sleeves onto it and doing up the nut loosely with your fingers.  A hole is then drilled into the wood and concrete you want to join and the whole assembly is tapped into place by hammer.  The nut is then tightened with a spanner until the required torque is reached.  As the nut is tightened it draws the bolt with the flared end up into the lower sleeve and spreads it against the walls of the hole wedging it into place.

Dynabolt/Sleeve Anchor
Dynabolt Parts

Trying to remove the bolt at this point is futile, the nut needs to be removed and the bolt tapped into the hole to release the pressure forcing the sleeve against the wall of the hole.  The sleeve will stay in place due to its own springiness, but it's now moveable.  I was lucky as I could still get at it.  If you can't somehow get to the sleeve you might as well cut the bolt off with a grinder.

In most cases your hole won't be deep enough for the bolt to be pushed under the level of the sleeve, this means you can't just grab the sleeve and pull it out, and pulling the bolt will just wedge the sleeve against the walls again.  The trick is to pull them both out at the same time by using a pair of vice grips to lock the sleeve onto the bolt.  This can then be pried out with a wrecking bar or similar tool.  You may need to reposition the vice grips a couple of times, but you'll get there in the end.

Dynabolt/Sleeve Anchor
Prying out the Dynabolt with Vicegrips
Dynabolt/Sleeve Anchor
Prying out the Dynabolt with Vicegrips

Once removed you should be able to reuse the hole.  In my case the hole was in the wrong place and the easiest option was to fill it and put the bolt in a different place.  You could probably reuse the bolt if you wanted to, but I had plenty of spare ones and didn't want to run into any problems.

The main advantage of a Dynabolt is also its biggest problem.  They are really hard to remove.  So if you make a mistake be prepared to spend a bit of time to get it out.  Take a couple of minutes to asses the situation and figure out the best course of action.  Not every application is the same, and different situations may require a slightly different method to remove the bolt.

Dynabolt/Sleeve Anchor
Damaged Anchor

1 comment:

  1. That's excellent mate. Thank you for the help!


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