I need to repair a stripped female thread in a piece of aluminum. Originally the thread was M7x1.0. I can enlarge the hole a little, but it's close to an edge, so not as much as might be needed.

What diameter hole is needed to support an insert capable of accepting an M6x1.0 screw?

  • Have you heard of Helicoils? Is that what you are trying to do? Also M6 is smaller than M7 - did you mean M8?
    – JPhi1618
    Commented Sep 27, 2019 at 17:54
  • That depends on the insert, naturally. Any product package should tell you.
    – isherwood
    Commented Sep 27, 2019 at 17:54
  • How thick is the metal where the hole is needed?
    – fred_dot_u
    Commented Sep 27, 2019 at 18:05
  • @isherwood: If there was a store near me that stocked metric I might be able to read such a package. I'm not the ass your comment Any product package should tell you suggests I am.
    – mr blint
    Commented Sep 28, 2019 at 12:40
  • 1
    @isherwood: sorry if I misread your comment as snark. I am searching for information before I buy so that I don't end up spending money on something that won't solve the specific problem, with its narrow tolerances. There is no brick-and-mortar shop near me that stocks these coils in the metric size(s) that might work for this application. If there were such a shop I would certainly read the package to get that information.
    – mr blint
    Commented Sep 30, 2019 at 13:51

1 Answer 1


For one of the best known thread repair inserts, Heli-Coils, (I've used them , not associated with them otherwise) an M6x1 insert has a maximum outside diameter of 7.95mm. Data here.

A better repair in many cases would be to have a welder (person) with a welder (machine) plug the hole, then drill it out and retap it to the size you actually want. Of course, if the original part was under-designed and that lead to thread failure, making it the same as it was won't ensure that it won't fail again the same way. If it's thin aluminum you need to find a good/skilled welder. If the part allows, welding or gluing a nut to it may be a better fix for a too-thin design.

  • Thanks for the heli-coil info. I will explore the fill with weld and retap option a little further. So far,the local welding shops I've called don't have any experience with aluminum and the required post-weld heat treatment, and I don't even know what alloy it's made of.
    – mr blint
    Commented Sep 28, 2019 at 12:45

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