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This is a base for an exterior umbrella. The screw isn't threading to the base anymore so I can't tighten it.

Is there an inexpensive way to "rethread" screws?

Right now, it just spins.

enter image description here

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    Is it stuck? Or does it spin without moving in/out? Oct 29, 2023 at 17:31
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    Tap and die sets. If the threads are badly damaged, will probably need to drill out the hole to next size bolt size.
    – crip659
    Oct 29, 2023 at 17:31
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    Title question can't looks like a typo?
    – Ecnerwal
    Oct 29, 2023 at 18:03

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Are you sure that's the right bolt? 3/8 UNC and M10-1.25 look kind of the same but are not compatible.

Oil, serioiusly just adding some oil can work wonders.

A new bolt can help too. bolts are cheap.

To rethread the hole you cau use a thread cutting tool called a tap, or since it's just rust in the way you can probably use a hardened bolt with a slot cut in in as a cheaper alternative, use lots of oil.

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    I think that a hardened bolt can improve your chances of restoring the threading without a tap. Less galling than any-old-bolt.
    – popham
    Oct 30, 2023 at 19:06
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That looks like a bolt that locks the umbrella pipe to the stand pipe, so wind does not do a Mary Poppins.

The cheapest way will be to drill right though both pipes and use a rod/bolt to lock them together.

A small hole though the end of rod/bolt with a hair clip pin will keep it from falling out.

Never worry about threads again.

A line painted on both pipes will help align the holes when placing the umbrella back in.

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Depends if you stripped the bolt or the nut.

I'd start with trying a new bolt.

You can use a tap and die kit if you figure out imperial vs metric and the thread size and bolt diameter 10-24, m10 1.25, etc.

You can rethread the nut to a larger diameter and get a new larger diameter bolt.

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    If you are very good(lucky), can sometimes change imperial/metric without needing to redrill the hole, just cut new threads.
    – crip659
    Oct 29, 2023 at 17:36
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Apart from replacing a damaged bolt, if applicable, or drilling out to a larger size and rethreading to take that size bolt (as already suggested) you can (for somewhat more money) drill out a stripped hole to a different specific larger size and insert a repair threaded insert to restore the original threaded size of the hole - this is commonly needed for things like spark plugs where there isn't a "larger size bolt" that will work.

HeliCoil® (I've used them, not associated, no endorsement) is one major brand of such inserts, and you can get a complete kit with the inserts, a proper size drill bit, the proper tap for the insert and a tool to put the inserts in with.

In this case, the "use a larger bolt and re-tap to suit it" option is probably more sensible (unless the bolt, rather than the nut, is stripped, where simple replacement and possibly chasing the nut threads, if damaged, with that size tap might work.)

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  • In this case there's enough material and no compatibility concerns, so saving the money and tap out to a bigger size is a much more sensible option than helicoiling it
    – Chris H
    Oct 31, 2023 at 9:18
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It depends on what exactly you mean by "can't tighten". Does the bolt jam or does it spin without making progress.

A "tap" cuts an internal thread, A "die" cuts an external thread. Taps and dies are not horribly expensive.

If a thread is damaged or contaminated, such that it jams up then running a tap/die over it can "clean it up" and make it functional again.

On the other hand if the bolt is spinning without making progress then that likely indicates that material has been lost, either through corrosion or mechanical damage. A tap and die can't put back missing material.

For the bolt I would suggest just replacing it, it's not valuable enough for any repair attempt to be worthwhile.

If the thread in the hole is too damaged to use, then you have a few options.

  1. Drill and tap it to a larger size, use a larger bolt.
  2. Drill right through the tube and use a nut and bolt instead of a bolt into a threaded hole.
  3. Install a thread repair insert, there are several different types, but the manufacturer should provide instructions.

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