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Is it possible to use molly bolts in concrete? They are generally described as for use in drywall. But I have a project that needs a hook or screw to be taken out from time to time, which is possible with a molly bolt. The load on the hooks would not be significant.

If it isn't possible, is there any other way of achieving this? Most anchors for concrete don't permit multiple insertions and removals of the screw.

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2 Answers 2

up vote 4 down vote accepted

A machine screw anchor is a good option for repeated removals and reinstallations. They're also available in standard thread sizes, so they can accept machine screws, eye bolts, or hook bolts. The downside is that you'll have to buy an inexpensive but specialized setting tool for each size of bolt you want to install.

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The installation process is much like that of the lag shield below, except that you'll have to use the setting tool (third step) to seat the machine screw anchor into the hole.

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A lag shield anchor may be another acceptable option, but it is not as "reusable" as a machine screw anchor. It creates a sleeve inside the hole in your concrete with threads for a lag screw to grab onto. When the lag screw is inserted, it expands the shield inside the hole.

The installation process:

  • Drill appropriately sized hole with a hammer drill and masonry bit
  • Remove concrete dust
  • Tap lag shield anchor into hole
  • Insert lag screw into lag shield and tighten

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The lag screw will still be removable, but keep in mind that many repeated removals and installs may eventually weaken the anchor.

Image Source

(I have no affiliation with either distributor, they just had good illustrations.)

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Lag bolt shields are not considered to be "re-usable" for repeated removals and re-insertions of the lag bolt. –  Michael Karas Aug 14 at 16:46
1  
@MichaelKaras: This manufacturer backs up my claim. Note that I did include a disclaimer that many repeated removals would weaken the anchor. –  Doresoom Aug 14 at 16:50
    
Thanks, machine screw anchors (I think also called drop-in anchors) are what I was looking for. Lag shield anchors were not as I can foresee almost daily removals and installs. –  Ian Cheung Aug 18 at 10:41

No, they won't work there... but there are similar expanding anchors that CAN be used in concrete, with threaded holes so you can remove/reinstall hardware at will. Don't get the lead (lead metal) ones, get the steel ones. You can even get some with male threads, onto which you could install a loop nut.

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Yeah!! The steel ones. One common brand name to look for is "Red Head". –  Michael Karas Aug 14 at 16:47
    
Is there a name for this type of anchor? I found the Red Head website but can't figure out which anchor would be the one I am looking for. –  Ian Cheung Aug 14 at 16:59
    
Their TruBolt anchors would work very well. Check your local hardware stores - they may carry TruBolts or another brand of similar anchors. –  TDHofstetter Aug 14 at 17:08
    
Thanks but looking at the Red Head website, TruBolt anchors are not the ones. TruBolt anchors are the type that leaves bolts coming out of the wall and the bolt is not removable. I figured out the type I was looking for from the selected answer, they are listed under Anchoring Solutions > Mechanical > Multi-Set II: Drop-In Anchors. –  Ian Cheung Aug 18 at 10:51

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