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:
(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.
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:
(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:
(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?