Expansion screw - installation

62_an · 2011-02-09T20:32:21+00:00

I'm going to attach a steel beam to a concrete slab and thought of using expansion bolts, so I bought Biltema's 10x120mm in hot-dip galvanized finish. But I have never used expansion bolts myself before, so I'm not very sure how they work. The screws didn't fall directly into the holes; I had to hit them quite hard. But when I try to tighten the nuts, the screws don't seem to grip properly in the holes. The worst are the holes where I had to hit the screws in hardest. I'm wondering if the concrete is too porous... the slab is 50 years old, and I know it has varying quality. Or is it poor screw quality? One screw came up about 20mm, so I loosened the nut and tapped it down again. It might grip slightly better after that. But no screw is gripping completely tight. I assume the screw should grip so that you can tighten "very" hard and not be "spongy." - How tight should you be able to tighten a 10mm screw? - How far should the screw come up out of the hole before it "grabs hold"? Help is greatly appreciated :)

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anaitis

#16

Construction veteran · Trollhättan , Västra Götaland

· 1 976 posts

12 Feb 2011 at 11:42 AM

anaitis

Construction veteran

Trollhättan , Västra Götaland
1,976 posts

12 Feb 2011 at 11:42 AM

anaitis said:
You must not drill too deep!
The lower part of the screw must reach the bottom of the hole.
To make the screw attach in the hole, you must hit it HARD so that it expands and gets stuck.

This turned out completely wrong!
I was thinking of a completely different system.

Expansion screw - installation

anaitis

anaitis

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