barrel threading

Discussion in 'Gunsmithing Forum' started by hmh, Feb 8, 2012.

  1. hmh

    hmh New Member

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    I am going to be purchasing a sound suppression device. And I am wondering if barrel threading is something I should tackle. I have unlimited access to a lathe, but limited experience with a lathe. On one hand I am fairly decent with most firearm related repair and it is something that I want to learn on the other hand I do not want to ruin a barrel. I know it has to be concentric with the bore and the only option I have is a live center. Do you think I should try?
     
  2. whiplash316

    whiplash316 New Member

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    cutting threads on a barrel should be done by a gunsmith, if you do not have one in your neighborhood, you could contact Brownells they should be refer you to one. If you have experience with machine work you might be able to complete the task.
     

  3. JonM

    JonM Moderator

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    if its not concentric your going to shoot holes in your time consuming to acquire suppressor.

    i would suggest getting a cheap beater barrel and action to practice with. shotout barrels can be had for super cheap from long range shooting folks ebay and some gunshops.

    you can make a straight rod to test concentricity before you shoot.

    so get some practice barrels and get after it until you feel comfy in trying on yours.

    i do a lot of diy on my guns but threading a barrel isnt something i would attempt without supervision by a really good gunsmith.
     
    SWSinTN likes this.
  4. hmh

    hmh New Member

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    The only competent gunsmith that i know of wants $150 + per. I have heard about some mail operations for the $30 range but am unsure about quality. And I will not get the knowledge of doing it.
     
  5. HotGuns

    HotGuns Member

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    I've done a few hundred barrels, so here is my two cents...
    Yes, the bore needs to be concentric. Using a live center is the way to go...the only way to go really.

    You don't really want to use the center itself, it is hardened steel and it will mess up the crown. First you need to make a centering spud from brass. Cut it so that it has both a 60 degree included taper on both the inside and the outside. You can do this easily by using a center-drill for the inner diameter and using the compound to cut the outer diameter.
    Cut it with a post that is the same size as the bore diameter.

    Slip this contraption over the center itself, while using the barrel to hold it in place. What you'll have is the spud inside of the barrel, (it only needs to be 1/4" long) and the brass centering up the barrel on the live center itself.

    This does three things. One, it protects the rifling inside the barrel and two, it allows you to re-crown the barrel without cutting into the live center and it also centers the barrel up on the bore.

    More often than not, the O.D. of the barrel will be a few thousandths off center. No big deal, just cut to the major diameter of the thread that you need. Be sure to use a parting tool to cut a relief in the threads so that the suppressor can shoulder up and tighten on the barrel itself, not the end of the threads. The shoulder must be absolutely perpendicular to the bore, because this is where the silencers both tightens up and aligns itself.

    If you have concentric threads, and a square and perpendicular shoulder in which to align the suppressor on, you will have no issues with misalignment.
     
  6. hmh

    hmh New Member

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    Thanks do you have a picture?
     
  7. HotGuns

    HotGuns Member

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    No.
    Give me a day or two and the next time I thread a barrel I'll take a few pictures.
    That'll make it easier to understand.
     
  8. hmh

    hmh New Member

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    Greatly appreciated.
     
  9. dhyayi

    dhyayi New Member

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    agree with you

    [​IMG] [​IMG]
     
  10. Ruzai

    Ruzai New Member

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    HotGuns is obviously more experienced and he is right about all of what he said, though there are different ways to achieve the same results.

    It all depends on what you have at your disposal.
    My way includes using a 4-jaw chuck, bore-indicator, and then a non marring live-center method close to what HotGuns mentioned.

    My question is, is this for a rifle or pistol barrel?
     
  11. hmh

    hmh New Member

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    Both 2 10/22 1 savage 93 1 22/45
     
  12. Ruzai

    Ruzai New Member

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    Well you definitely will need the non-marring cover for the live center in that case. You can get away without using one on a pistol barrel as long as you take very light cuts and know what you're dong from what I've heard but I wont be trying any time soon without the brass cover for the live center.
     
  13. HotGuns

    HotGuns Member

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    Crown Savers.
    Here is a pic from Brownells. I just make them, with a longer post on them.-
    [​IMG]
     
  14. HotGuns

    HotGuns Member

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    Here is a picture of the ones I make. They are a whole lot cheaper.
    [​IMG]
     
  15. hmh

    hmh New Member

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    Thanks any more hints or info greatly appreciated.
     
  16. hmh

    hmh New Member

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    Me and a machinist friend are going to tacked it. Does anyone have a diagram of 1/2 28 or where I can get one.
     
  17. Ruzai

    Ruzai New Member

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    No clue where you'd find the diagram.

    Any amount of threading you plan to be dong beyond this particular project, you might think of investing in a TPI gauge.
     
  18. hmh

    hmh New Member

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    I have one and I am not worried about the threads. What I am wondering about is the length of the threaded area, the relief, how deep I should cut the relief, ect. I have heard .400 for the thread length but I do not know. I shouldn't have been as vague.
     
  19. CubDriver451

    CubDriver451 New Member

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    in response to those advocating the use of a live center and a crown insert/protector- I have never used this method, and will not say that it is an improper method to use, but I do think it is not the best method to use. IMHO, the best method is to use a lathe that has a short enough headstock and large enough spindle hole that you can pass the barrel through the headstock and indicate the center of the bore of the barrel on both ends. This will require that you make a "spider for" the spindle of your lathe. This is nothing more than a collar with four adjustment screws that is mounted on the end of the spindle (opposite the chuck). Use a four jaw chuck and indicate in the bore, with only a few inches of barrel protruding from the chuck. This insures that the bore of the barrel is now concentric to the machine.

    Using a live center will only insure that the bore is centered at the point that it meets the live center. This is not the same as being concentric, because you are still relying on the outside diameter of the barrel on the end held in the chuck. Indicating on the OD of the barrel does not guarantee that you will be working concentric to the bore. I have seen barrels that were not concentric (OD to Bore) by as much as .015".

    The crown protectors may work, and you may never have a problem with this method, but it really is not the "best" way as you are still relying the the OD of the barrel to be concentric to the bore. If your lathe headstock is not short enough, or the spindle hole is not large enough to pass a barrel through, a better alternative, IMHO, is to use a center mounted, and indicated to perfection in a four jaw chuck, and then drive the barrel with a lathe dog. The downside to this method is that you are now relying on the breech face of the barrel to be cut square to the bore. Once again, I have found this to rarely be the case, but having tested many barrels over the years for concentricity, I have found that this method is superior to using the OD of the barrel in a three or four jaw chuck.

    While any of the methods talked about will probably work for most applications, rifle accuracy is affected by a host of variables. Getting the crown perpendicular to the bore can make a big difference by causing the gasses behind the bullet to exit the muzzle evenly, rather than offset by whatever amount the crown is not square to the bore. This can slightly upset the bullet as it leaves the barrel. The ONLY way to get the crown square to the bore, for certain, is to indicate both ends of the bore. This holds true for threading a barrel too. It may or may not make a difference, but using this method, I KNOW that I have done everything that I can do to make the crown, threads and breach face cuts as perfect as I can. This cannot be said of any other method, as you will be relying on the OD of the barrel being concentric to the bore with any other method.

    JW
     
  20. CubDriver451

    CubDriver451 New Member

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    Dig into a copy of Machinery's Handbook. There are tables for pretty much all common threads and formulas for calculating non-standard threads. Or you can just do what I do, and fit the threads to what you are attaching to the barrel. This is simply done by getting the threads close to the proper depth and then working in VERY SMALL increments on finishing passes until you get a nice, close fit.

    Single pointing threads is not difficult, but to get a good fit requires patience. Don't rush, take your time and do it right.

    JW