11

What are some proper screws or anchors to use for affixing something to a steel walk-in door?

The example for this question will be attaching an automatic closer to an exterior steel door. The door is a typical residential steel walk-in door, which is "hollow" (foam core) and made of a rather thin-gauge of steel: 24 gauge = 1/40" = 0.0209 inch = 0.53 mm.

Here's a cutaway-view of an example steel door:

Steel door hollow foam core cutaway
(Image from provia.com)

The steel being so thin creates a problem. The door closer in question came with machine screws and tells the installer to use a 12-24 tap, which I found odd. Maybe they expect a thicker gauge of steel? I used my tap and the screws stayed in for a few months, but someone tried pulling the door closed faster than the closer allowed and the resistance from the closer caused the top screw holes to blow-out. The bottom ones are nearly ruined as well.

Door closer screw holes

Door closer machine screw

Door closer hole blown out


I would use anchors of some sort, but I can't seem to find any that are made to work on such an incredibly thin surface. Most anchors I see have a minimum thickness of 1/8 inch, and even then I would question them:

Drywall anchors
(Image from yindigoarya.com)


The only anchors I see that claim to be for "hollow-doors" are this type, but they seem to be made for hollow wood doors commonly used for closets and such. They don't seem right for this job:

Hollow door and drywall anchors
(Image from homedepot.com)

Maybe they just don't make anchors for this type of thing?

I was thinking I could use "thicker" threaded screws like wood screws. I'm not sure how much that will help here. I worry it will just blow out the hole again and leave a larger hole behind. Plus, a rather thick wood screw would be needed since the holes are already wide.

What's a safe way to fasten this closer to reduce the risk of blowing out the holes even worse?

6
  • Have you considered just buying a new door?
    – nick012000
    Mar 23 at 4:10
  • 1
    @nick012000 - What would that solve? I'd end up right in the same boat I'm in now unless I do something different.
    – Bort
    Mar 23 at 13:27
  • 2
    "What would that solve?" Well, if you buy a more solidly-constructed door, it might not break when someone closes a bit too hard.
    – nick012000
    Mar 23 at 13:33
  • @nick012000 - Ah, a new thicker gauge door. That's a possibility, but I had grabbed the only steel door of the size and style I wanted at the local hardware store. For thicker gauge I'd have to go from "residential" to "commercial", and then they no longer look like they belong on a house/garage. They look like the back door to a fast food restaurant. On top of that, the cheapest doors are around $150, and I'd probably have to spend much more. I'd have to pay that, get the door home, swap it with the old one, paint it, install the opener, and then hope the threads don't strip again.
    – Bort
    Mar 23 at 14:05
  • Have you considered fitting/gluing a plate of thicker steel onto the face of the door, and screwing into that? Or even plywood and wood screws Mar 24 at 11:22
14

This appears to be well suited to a rivnut installation. The threaded insert is placed in a hole sized appropriately to the insert, the tool is used to compress the portion inside the door and the threads remain for the bolt to engage. Rivnuts are best used on thin sheet material.

Rivnut tools can be quite expensive, but those are primarily for production grade or professional use, while home improvement level tools are less durable and more affordable:

Amazon rivnut tool

amazon tool image

This kit would have nearly a lifetime supply of inserts, although the tool may not last a lifetime. I have this specific tool and it works well.

4
  • Also called a nutsert (nut insert) - not sure if that is a regional thing or what. McMaster-Carr is happy to search for various versions of the terms, but the page shows 'Rivet Nuts' at the top.
    – Jon Custer
    Mar 23 at 13:10
  • The nutserts I use are designed to be melted into place, rather than a rivet-type compression, but as with so many aspects of the language, meanings can vary.
    – fred_dot_u
    Mar 23 at 17:57
  • These nuts only have an overlap of about 1/16" / 2mm, so from this thin steel sheet they would most likely rip out soon. And since there's no access to the inside of the material, even adding a washer isn't possible.
    – WooShell
    Mar 24 at 11:49
  • I'm going to mark this as the best answer for now. Rivnuts don't require drilling through both sides of the door (which would be unsightly). Toggle bolts would also avoid that issue, but they would likely cause visible denting to the interior side of the door due to the wide span and concentrated contact of the "wings" against the inside of the steel. I have installed rivnuts for now and they seem to be holding well. I will update this question if rivnuts fail.
    – Bort
    Apr 1 at 16:51
15

Any type of threaded screw will eventually pull out. I'd think about using some bolt and cap nuts. You'd have to drill right through the door and can probably use the same holes on one side. I'd think about adding a few washers on each side for a little extra strength.

enter image description here

9
  • Well it may not look as pretty with something coming through the other side, but it certainly looks more robust.
    – Bort
    Mar 22 at 20:50
  • @Bort Get some close matching paint and dab some on the backs of the screws and you won't even notice them.... nail polish works great because it comes in a million different colors.. :-)
    – JACK
    Mar 22 at 21:09
  • 5
    I'd probably go as far as installing a small plate on the other side, that foam looks flimsy. But yeah. this. Mar 23 at 10:29
  • 1
    I see an issue there: The bolts compress the door, as they are only supported by foam. So the bolts aren't under tension anymore and get loose..
    – Martin
    Mar 24 at 10:21
  • 1
    BTW: in North America, these fasteners are often called "sex bolts" (I guess since both mating parts come in the same package?) Mar 24 at 23:18
7

Since security could be a concern, I'd suggest a plate on the outside with square holes punched, or round holes drilled to accept carriage bolts that go all the way through the door and nuts on the inside.

This will prevent anyone from being able to remove bolts from the outside.

If you drill a clearance hole through the plate, you can use a file to square up the corners to hold the shoulders of the carriage bolts. If you drill a large enough hole for the shoulders to go through, then you have nothing to hold the bolt while you tighten the nut on the inside.

If you can find a metal fabrication shop in your town, I'm sure they'd be able to make some square holes for you. Of course, it would cost a few more bucks, but that's the price of progress...

5
  • 3
    If you mean security against thieves, I don't now why they would want to remove a door closer. If you mean security in the sense of "unlikely to break off", then this is an excellent solution. +1
    – David42
    Mar 23 at 15:09
  • I suspect that FreeMan thinks this is for magnetic catch, not an autocloser
    – CSM
    Mar 23 at 16:16
  • @CSM I realize that this is for a door closer, not a magnetic catch. If you don't think it'll work for that purpose, feel free to offer your own suggestion or even down vote mine.
    – FreeMan
    Mar 23 at 16:24
  • You'll have to reinforce the thin metal of the door and spread the 'load' over a larger area. An additional two plates sandwiching the door (and painted to match the door color) will provide a stronger surface for which to run through-bolts through. You really can't attach the closer to just one side of the door, I fully expected to see the metal under the closer to have been warped by the stress. Fortunately only the screw holes were damaged and that won't be a concern or noticeable when you install reinforcement plates.
    – Arluin
    Mar 23 at 21:17
  • @Arluin I did specify a plate on the outside. An additional one on the inside certainly wouldn't hurt.
    – FreeMan
    Mar 24 at 11:21
2

Could I suggest not using screws at all, and using something like 3M VHB (Very High Bonding) tape? Some varieties are stronger than rivets, at least according to 3M, and is used in a lot of places where rivets used to be used, such as in attaching various parts of cars to the frame, or in bonding parts of airplane wings together. See https://www.3m.com/3M/en_US/vhb-tapes-us/. They do require a few days to set before the bond is permanent, however.

6
  • 2
    Thanks for the suggestion Kevin. I'm not sure what you mean by "garage door opener", do you just mean a regular door opener? I don't think they make residential steel doors made for closers. As for using tape, I was not aware there was tape stronger than rivets. I'll look in to that. FYI, it's best not to include link-only answers, as links often go dead and then your answer loses its content.
    – Bort
    Mar 23 at 14:55
  • I've had door closers that were strong enough that when wind started to tug on the door, it ripped out the bolts, so no tape is going to be stronger than that. Also, a garage door opener expects 8-10 feet of travel, not 18-24 inches, and I've never seen a walk-in door that would already have those connections. Mar 23 at 17:43
  • Actually, tape can be better than bolts for "ripping off". I saw a news article where VHB tape held road signs just fine when the similar signs using conventional fasteners were ripped off in a storm. It spread the load over many square inches rather than focusing the force.
    – JDługosz
    Mar 24 at 14:21
  • Sorry, I misread the initial question, and was confused. I still think VHB tape might be appropriate, however. Expanding the answer. Mar 24 at 14:46
  • 1
    @FreeMan Yes, I was in the process of doing so when you made the request. Mar 24 at 14:53
2

Have you considered old-fashioned butterfly anchors (AKA toggle bolts)? They're fairly burly, cheap, widely available, and don't require any specialty tools, equipment, machining, etc. Note that for a foam-filled door, you would need to do some fiddling to make sure the "wings" can actually open up in there, but just sticking a scribing tool in the hole on an angle and digging around to break up the foam should do it. (Or a nail held in a pair of pliers, if you don't have a scribing tool lying around.)

Toggle bolt in drywall
(Image from diynetwork.com)

Decent quality, decent sized butterfly anchors should hold easily as strong as "rivnuts", likely more so, as they spread the load much farther over the surface. And not needing a specialty tool to install them is a bonus.

FreeMan's approach of a backing plate with carriage bolts all the way through would be far more robust, of course, but it's also far more expense and effort, and leaves you with a big ugly backing plate on the exterior of the door. If you were installing a mag-lock to secure the door against break-ins, I would suggest the backing-plate-and-carriage-bolts solution. For a door closer that just needs to withstand some casual abuse, butterfly anchors should be plenty.

And don't consider tape. It's just possible, maybe, that a modern adhesive like JB-Weld's 2-part epoxy for metal would be up for this job, but... that's a small surface area, on an uneven and flexible surface covered in paint. To give any adhesive even a fighting chance, you'd need to wire-wheel down to bare metal, clean it with solvents, and then clamp (or bolt) the glue joint for hours to let it fully cure before using it, and even then it would be unlikely to hold as long as the original machine screws did. As for VHB tape, it's good stuff, but this is not a problem you're going to solve with tape.

3
  • I think toggle bolts could work. One issue is that the smallest toggle bolt I can find for sale is "1/8 inch". (Do they make any smaller?) They say on the box to use a 3/8" drill but I just measured one to be 7/16 (11mm) at the widest part. That would require the size of the holes in the door to be doubled. The holes would be a bit close to each other, but perhaps not a big deal.
    – Bort
    Mar 23 at 19:59
  • Toggle bolts do require a pretty big hole, it's true. Fortunately, since the load is supported by the whole wingspan of the toggle, the holes can be really close together without causing a problem. Unlike putting screws directly into the metal, toggle bolts don't rely on having enough "meat" to grab right at the edge of the hole. I would use the biggest ones that will fit through the holes milled in your door closer. (Just orient the toggles so they're roughly parallel when putting them in, so they don't tangle each other up.)
    – Askeli
    Mar 23 at 20:33
  • Do take note, also, that when using toggle bolts, it's only the hole into the door itself that needs to be drilled out big. The holes in the door closer only need to accept the shank of the bolt, not the whole toggle.
    – Askeli
    Mar 23 at 20:35
1

Another thing you might try is to create an "adapter plate" to spread the load of the door closer over a larger area of the door.

As you've already experienced, that this sheet metal is not capable of supporting the door-closer forces centered at the 3-4 screws on the closer.

A piece of aluminum plate could be used to spread the load to 5-10 screws over a larger portion of the top of the door. Then the closer could be screwed to the adapter plate.

This would spread the door closer forces over a larger number of screws lessening the load on any single portion of the thin door material.

-1

I would recommend something this:

enter image description here

It is for wood, but I think it will do fine with thin steel. Name should be coach bolt.

Drill hole through door big enough for thread on the bolt to pass freely. But too small for the rectangular extension under the head. Insert bolt from outside of the door and screw nut from inside. The extension should extend round hole to square and prevent the bolt to slip as you tighten nut.

2
  • In what way (other than providing a picture of the bolt) is this different from my answer posted yesterday? If you have something to add, please edit it in - if it's good advice, I guarantee you'll get my up vote. However, simply repeating other's answers isn't the quality that we're looking for at StackExchange.
    – FreeMan
    Mar 25 at 11:16
  • I probably misunderstood, that you suggest aditional plate on door outside.
    – tmiso
    Mar 26 at 12:30

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