Fixing a slightly oversized helicoil by swaging
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  1. #1
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    Default Fixing a slightly oversized helicoil by swaging

    Can anyone show point me to any handbook or spec that allows the use of swaging to repair slightly oversized helicoil threads?

    The issue is that a supplier thought it was a good idea (after it was verified the NOGO side of the thread gage spun in 4 timesvs the limit of 3), to take a threaded form tap and swadge the threads slightly and then re-tap with the appropriate tool. Now the thread hole is "within spec" but in my experience this was not a conventional method of repair for this issue.

    I am actually trying to give them an out, more or less, but I can't find it anywhere. They say their expert tool maker said this was a tried and true method but again, it seems like something I would do in my garage on my lawnmower block but not an expensive aluminum part.

    Thanks for any help.

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    What do you mean by swadging? If you mean taking a bearing ball setting it on the threads and taping it with a hammer so the no-go doesn't thread in, that is not a "Tried and True Method". It is a skeezy way to try to get bad parts past QC and would cause me to think real hard about sending them any more work.

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    In my opinion you have gotten some wonky information from someone. As Kenton said, you can put a ball bearing in a threaded hole and smack the crap out of it to tighten up the first couple of threads. Just like you can take a threaded nut and put it on an anvil and smack the crap out of it to make it tight on a bolt. Both of which are useful in very few circumstances. I would think doing this with a helicoil would be disingenuous. The reason to use a helicoil in the first place is to fix a thread that already has a problem. I have never heard of swaging threads with a form tap. Maybe there is a process for doing that but I don't see how it would work.

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    Try a different thread gage. Yours might be worn.

    Put a bigger chamfer on the hole, so your gage only goes 3 threads deep.

    Put the part in the freezer, and snuggle the thread gage up against your
    privates until it warms up, that'll probably make it pass.

    Probably better off just leaving it as it is instead of messing with it.
    Its not like the thread gage fell through the hole.


    Are the parts getting anodized? That'll bring those holes right in. maybe.

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    I never heard of swadging the threads with a form tap either. I figured it was exactly like putting a Ball bearing and tapping the threads to give a false reading with a GO/NOGO gauge.If there was the slightest chance anyone else in the community heard of it, I wanted to ask.

    Turns out that's what they did. I've seen a lot, heating and cooling parts, using less accurate gauges...never had a shop openly admit to this method. They are arguing that they did not violate the drawing in anyway. So going back up to inspect with our gauges and ensure the minor diameter is still in.

    Bobw,

    Yes the parts are getting type 3 hardcoat less the threaded insert holes. the threads just get Iridite. They used several gauges.
    If I was the inspector on the job I would have had them reapply the Iridite in front of me and tried again. I bet it would have been just fine.
    I'm just the one dealing with the information now. Lucky me.

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    pull the part
    find a new supplier

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