Hi everyone (noob alert)- I need to put a threaded bolt into a fresh new hole I have drilled into a piece of metal but how do I put in threads which match this particular bolt? Thanks

  • What is the purpose of the hole? What material is it you want to thread?
    – GdD
    Sep 27, 2017 at 14:04
  • it's a block of very thick steel. a small hole not too big at all.
    – MathNYYB
    Sep 27, 2017 at 14:43
  • 4
    So how is this motor vehicle related @MathNYYB? I'm not being pedantic, it's about understanding the overall thing you are trying to achieve, otherwise you might not get the answers you really need. What is this actually for?
    – GdD
    Sep 27, 2017 at 14:45
  • Seems like this would've been more appropriate on: diy.stackexchange.com Sep 27, 2017 at 20:35
  • How thick is the "piece of metal". What is the size of the "piece of metal"? Is the "piece of metal" permanently attached to something (like a car) or is it a freestanding thing that can be moved? Sep 27, 2017 at 21:53

2 Answers 2


Making threads is done with two tools known as a Tap and a Die. The are sold individually or in sets. To make threads in a hole, you need a tap. Those are the items in the image that look like a cross between a bolt and a drill bit. In fact, that's what they are. As you use the handle to turn them into the hole, the tapered flutes cut threads into the walls.

Note that each tap size needs a very particular hole size, and many are sold with matching drill bits because some sizes are just a little different than the typical set of drill bits will contain.

Also, each size will have a minimum thickness. These are not for use in sheetmetal. The metal needs to be thick enough to have at least a few threads cut into it or the bolt would easily rip out. The thickness needed depends on the bolt size and the strength requirements.

The dies (plural spelling?) are the circular pieces and they are used for making threads on the outside of a bar (to make a bolt).

Using these tools takes a little practice and some patience. Its possible to break a tap off inside a hole, and then you have a tough situation.

enter image description here

  • 2
    you can't emphasize the practice part enough. It is practically guaranteed a newbie will break at least one tap while learning (especially a the smaller sizes and especially going into steel).
    – agentp
    Sep 27, 2017 at 16:48
  • @agentp That’s true, and I would suggest the OP learn more about it and practice on scrap first.
    – JPhi1618
    Sep 27, 2017 at 16:52
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    Also look very carefully at the taps in the image - the tap on the rhs is a botoming tap to finish the thread to the depth of the hole , the other three are "starting" taps to start the thread ...
    – Solar Mike
    Sep 27, 2017 at 18:58

The tap & die answer is accurate, and as for your concerns about the threads matching, maybe this will help you choose the correct thread type/count so it should be no issue. Threads for screws, bolts and nuts vary due to type & intended application and are very precise. Dies and taps have a numerical indicator on them revealing the size and thread count they are gauged at. Lower thread count=less ridges per inch and a "looser" thread pattern, higher count= "tighter" pattern and more ridges per inch, and these are standardized across the industries that utilize these fasteners. Your bolt`s size and thread count are easily measured/verified, making matching it to your needed tap tool just as easy, and being standardized means you can buy the tap you need from any who sell tap & die equipment and be assured an accurate fit.

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