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I’m getting the impression that self-drilling screws should not be reinserted into original hole.

This is sheet metal thread into composite and metal backing.

The application is interior and exterior to an RV which experiences extreme vibration.

Replaced screws fall out.

Proposed solution is to oversize the replacement screw?

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  • When you reinsert the screw, do you first turn it anticlockwise until it drops into the already-formed thread? (Some screws have two threads and you have to turn it back until it falls into the deepest thread.) If not, it will certainly cause damage. Jan 25 at 17:29

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Self-drilling screws cut a hole sized for the screw shank. The threads still self-cut. Therefore, assuming no initial overtightening or other abuse, they can be reinstalled with minimal loss of hold.

There may be diminished resistance to spin-out, though. I suggest lock washers or something like epoxy to prevent rotation.

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There are generally three methods to deal with a screw that doesn't hold:

  • Fill the hole

This generally works well with thick pieces of wood, typically using toothpicks and glue. Not usually a practical option with metal or plastic.

  • Move

An inch or two up, down, left or right. Works very well for some things, but not if the screw position is critical.

  • Larger Screw

Treat the existing hole like a pilot hole driven for a larger screw. When screwing into wood, you can increase the length as well as the diameter of the screw. When drilling into metal, generally the length doesn't matter, just the diameter.

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  • Thank you, are self-drilling screws a problem to reuse?
    – DavidJ
    Jan 25 at 15:43
  • The screws can be reused unless they are damaged (e.g., bent, or tip broken). But they just won't work in the same hole again. Use them elsewhere. Jan 25 at 15:52

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