I want to somehow get an M5 insert into a 7.5mm diameter hole in solid steel. (The hole has already been drilled with 7.5mm DeWalt cobalt-tipped drill bit.)

Is there such a thing as a threaded insert that is suitably constructed to be able to go into solid steel? Some have external threads, some have that rough/raised diamond pattern on the exterior instead. I'm not sure what might work. How about something I could hammer in, if the insert's diameter is finely tuned to be just above 7.5mm?

Here are some threaded inserts "for metal and plastic". I have no idea if something like this may work, or how to insert it properly.

Any advice is much appreciated. Thanks

  • 1) figure stuff like this out before cutting any material, and 2) why require inserts and not just tap the hole? Usually inserts are for soft materials. Commented Apr 10, 2021 at 21:11
  • 1
    Would be tough to tap an M5 in a 7.5mm hole. :) Why not a larger screw?
    – isherwood
    Commented Apr 10, 2021 at 21:16
  • Perhaps if you explained the purpose/function for the M5 threads there may be an alternative solution.
    – Alaska Man
    Commented Apr 10, 2021 at 21:22
  • @whatisname: 2) I've no idea tbh, but I'm assuming from what you've said that this is the better thing to do. I had to Google "tapping" to understand what this actually means!
    – teerev
    Commented Apr 10, 2021 at 21:26
  • 1
    You shall state what is the application to get meaningful responses. Please provide us with more clues.
    – r13
    Commented Apr 10, 2021 at 21:26

2 Answers 2


Sounds like you're asking for a drop-in solution for an existing hole and screw size. That's a tall order. I doubt you'll find it, but if you can stand a bit of DIY here are a few options...

  1. A Helicoil (repair coil) normally requires existing threads, but you could epoxy it into place. I'm not sure an M5 will fit your hole, though. You'd want to run your screw in and out before the epoxy sets to clear any squeeze-out.

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  1. A threaded sleeve or bushing could work, but again you'll probably need to epoxy it and possibly drill larger.

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  1. Tap it for a larger screw. You haven't said what you're mounting, but it may accommodate a thicker screw with or without slight modification. An M8 might work well with the existing hole.

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those inserts will work, but if it's going into steel you'll need to cut a thread in the steel to accept the insert, the will self-cut aluminium but not steel.

For that steel you'll need a tap that matches the thread on the outside of the insert (and a tap handle to turn it, and some cutting oil).

The inserts should come with a installing tool or you can use a bolt and a nut.

Were I in your situation I would go to a bolt shop and use their expertise, they will have the inserts and the apropriate tap etc.

If you're buying online you'll need to measure the thread on the insert and then order the correct tap.

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