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Thread: Brass pipe mandrels

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  1. #21
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    Quote Originally Posted by megafiddle View Post
    [/I]I am starting with an oversize bushing, so the inside diameter is undersize at 0.575", but then so is the barrel, at 0.575". So I should be able to achieve a clearance of 0.001". I could aim for 0.003", which should accommodate the lock up angle, but I would rather keep the clearance at minimum, and relieve the bushing to allow for lock up.

    -
    Fine ... but that's not mid-spec, which is what you wrote that you were aiming for.

    Quote Originally Posted by megafiddle
    I am indeed making a mid-spec A1 type barrel.
    Hawkmoon
    On a good day, can hit the broad side of a barn ... from the inside

  2. #22
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    Quote Originally Posted by brickeyee View Post
    He is trying to create a typical piece of production junk.

    A waste of time.
    Neither of those statements has any merit.
    When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind. [Lord Kelvin]

  3. #23
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    Quote Originally Posted by brickeyee View Post
    A scraper is more than adequate.

    It also provides more control than sanding.
    I've never used a scraper (hand broach?). So I'm not sure if I could do a better job with it.

    If my idea works, it ought to produce a practically perfect angled bore in addition to the original straight bore. This would not be sanding by hand in the sense that the bushing and tool are hand held; one of the two (not sure yet which would be better) will be clamped, and the other carefully guided.

    -

  4. #24
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    Quote Originally Posted by Hawkmoon View Post
    The M1911A1 was mass produced. The barrel bushings were not fitted, and they were not relieved.
    Couldn't a combination of in spec parts result in a minimum 0.001" clearance though? And result in springing?

    Kuhnhausen's approach to this condition, at least for replacement bushings fit to 0.001", is to add relief at lower front and upper rear of bushing bore.

    -

  5. #25
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    Quote Originally Posted by Hawkmoon View Post
    Fine ... but that's not mid-spec, which is what you wrote that you were aiming for.
    That's true, but a mid-spec barrel diameter is impossible in this case, and so a bushing needs to be fitted, as a minimum-spec bushing would provide 0.006" clearance.

    To be fair, the barrel diameter specs and bushing specs could be altered (both lowered by 0.004") to have the same spec relationship as the true A1 parts. At best then I would have 0.002" clearance.

    So strictly speaking, my barrel diameter to bushing fit is not mid-spec.

    -

  6. #26
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    Quote Originally Posted by megafiddle
    Couldn't a combination of in spec parts result in a minimum 0.001" clearance though? And result in springing?

    Kuhnhausen's approach to this condition, at least for replacement bushings fit to 0.001", is to add relief at lower front and upper rear of bushing bore.
    Yes, as I stated previously, a combination of a basic dimension barrel and a basic dimension bushing will result in a clearance of .001". I don't know if that would result in springing.


    Quote Originally Posted by megafiddle View Post
    That's true, but a mid-spec barrel diameter is impossible in this case, and so a bushing needs to be fitted, as a minimum-spec bushing would provide 0.006" clearance.
    You are the one who wrote that you want to create a mid-spec A1 condition, not me or anyone else. Since mid-spec is more clearance than .001" you can easily create the same clearance as mid-spec with your parts, by opening up the bushing a bit more.

    To be fair, the barrel diameter specs and bushing specs could be altered (both lowered by 0.004") to have the same spec relationship as the true A1 parts. At best then I would have 0.002" clearance.
    Which is still not equal to mid-spec. See post #12.

    So strictly speaking, my barrel diameter to bushing fit is not mid-spec.
    That's what I've been saying.
    Hawkmoon
    On a good day, can hit the broad side of a barn ... from the inside

  7. #27
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    Quote Originally Posted by Hawkmoon View Post
    Question: If all you want is a carbon steel barrel with a GI fit, why didn't you just buy one of these? http://www.e-sarcoinc.com/newgipatte...acpbarrel.aspx

    Or one of these? http://www.e-sarcoinc.com/451911barrel5roto.aspx
    Simple. That's not all I wanted. The purpose of the project is to fit a barrel. An A1 spec barrel was just a reasonable choice for this first attempt.

    If I had a milling machine, I would have tried fitting a match grade barrel, but my hand filing skills aren't up to that level of precision yet.

    I also looked around for carbon steel barrels to work with, and all I could find were the Swenson. I wanted something of better quality.

    -

  8. #28
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    Quote Originally Posted by Hawkmoon View Post
    Yes, as I stated previously, a combination of a basic dimension barrel and a basic dimension bushing will result in a clearance of .001". I don't know if that would result in springing.
    I was basing that on Kuhnhausen Volume II pg 115, where he states that at 0.003" mid-spec clearance, the clearance falls to zero at 100 percent lug engagement. So presumably, it would not be enough at 0.001" or even 0.002".

    Quote Originally Posted by Hawkmoon View Post
    You are the one who wrote that you want to create a mid-spec A1 condition, not me or anyone else. Since mid-spec is more clearance than .001" you can easily create the same clearance as mid-spec with your parts, by opening up the bushing a bit more.
    Actually, no. I never said mid-spec condition, only mid-spec barrel.

    -

  9. #29
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    Quote Originally Posted by megafiddle View Post
    I was basing that on Kuhnhausen Volume II pg 115, where he states that at 0.003" mid-spec clearance, the clearance falls to zero at 100 percent lug engagement. So presumably, it would not be enough at 0.001" or even 0.002".
    -
    The Kuhnhausen books are valuable resources, but they are known to contain errors. Unless someone can explain this to me, I would have to say that the statement makes no sense whatsoever. Clearance is clearance. What happens at the chamber end of a barrel can't change the sizes of the muzzle and the bushing, so the clearance remains the same irrespective of lug engagement.

    Let us know how it turns out.
    Hawkmoon
    On a good day, can hit the broad side of a barn ... from the inside
    Last edited by Hawkmoon; 21st September 2017 at 06:05.


  10. #30
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    Quote Originally Posted by Hawkmoon View Post
    The Kuhnhausen books are valuable resources, but they are known to contain errors. Unless someone can explain this to me, I would have to say that the statement makes no sense whatsoever. Clearance is clearance. What happens at the chamber end of a barrel can't change the sizes of the muzzle and the bushing, so the clearance remains the same irrespective of lug engagement.
    I'm certain that Kuhnhausen is referring to the clearance at the upper rear and lower front of the bushing. So the 0.003" clearance (for example) is still there at full engagement; except now the 0.003" is all at the lower rear, and upper front, with none left at the upper rear and lower front. It is at these last two points that the clearance falls to zero. It's just redistributed.

    Quote Originally Posted by Hawkmoon View Post
    Let us know how it turns out.
    It will be a while, but certainly.

    -
    Last edited by megafiddle; 21st September 2017 at 18:46.


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