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Thread: Bolt flutes

  1. #21
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    Quote Originally Posted by Butch Lambert View Post
    You sell the sizzle, not the steak!
    I prepare sizzled steak for myself, but sell sizzled steak with a fancy parsley garnish!

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    G'Day Fella's,

    From my experience with bolt (or barrel) fluting, here's my "Two Bob's" worth.
    You can have two types Straight and Helical.
    The reason for Helical flutes, on a bolt body over the Straight version, has more to do with reliable ammunition feeding than any thing.
    On a bolt with Straight flutes, the ammo in the magazine can engage with the flute on the underside (at 6 O'Clock), of the bolt body, and can cause difficulting in bolt rotation. This is not an issue with Helical bolt body flutes.
    This can be addressed, by having a intermitent/interupted straight flute, on the underside of a bolt body.

    The other thing to consider is weight.
    Given this, "the shortest distance between two points, is a straight line".
    When Helical flutes are cut, this intails taking a longer path/distance and thus, removes slightly more material and weight, from the bolt/barrel, than with Straight flutes.

    Appearance seems to be another reason, for bolt/barrel fluting.

    In my esperience, if you want a ultralight rifle, for extreme mountain hunting (like Tahr Hunting in New Zealand's, Southerm Alps), you will appreciate removing every ounce/gram you can, from your kit (back pack (and it's contents) Rifle, scope base, scope, etc).

    Hope that helps

    D'h!
    Homer

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    Correct answer. It gives dirt a place to go without scratching the receiver up. Does nothing for the chamber, though.

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    Trevor, if you're still out there, is there a way to do this with a small gunsmith lathe?

  7. #25
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    Quote Originally Posted by Marcia View Post
    Correct answer. It gives dirt a place to go without scratching the receiver up. Does nothing for the chamber, though.
    I’d say it gives places for dirt to settle on, then be dumped into your magazine and trigger when opening the bolt.

    With a smooth bolt body, there’s no need for a place for dirt to go, because it never would have settled on the bolt in the first place.

  8. #26
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    Quote Originally Posted by Marcia View Post
    Trevor, if you're still out there, is there a way to do this with a small gunsmith lathe?
    Yeah, there are a couple different ways you could cobble together some indexing system and a means to synchronize the turning of the lathe spindle so it is relatively coordinated with the movement of the lathe carriage.

    This isn't exactly a new use for a lathe, there are books written many many years ago on the subject of Ornamental turning, that cover such, in depth. There are a lot of mentions of the sort of work in the British Model Engineering magazines too.
    You should be able to find copies of Holtzapffel's book on Complex and Ornamental turning in the online repositories of out of copyright books, or try your local library to inter-library loan a copy.

    Then you need to arrange either a milling or grinding head to be mounted where it can do you some good.

    The most basic way to operate, is to look at your helix as a thread pitch, and increase the thread pitch gearing until you get the angle you want. You will have to drive the leadscrew, rather than the spindle, as it will be geared very much higher than it was when cutting threads. Look at the pitch of the leadscrew, figure out, for instance, how many times you need to crank the leadscrew around to advance the carriage 6 inches, while rotating the lathe spindle once. Select gears accordingly.

    There were jigs that used pulleys and steel cables to turn helical patterns on wood lathes. Similar could again, be rigged up.

    In either case, I suspect that I would choose to use a grinder or router with mounted stones as the cutting tool. Certainly cheaper than a tool post grinder, if nowhere near as precise.

    None of the methods I can think of, to do it with a lathe, would be particularly easy to work with, some amount to being a massive pain in the arse, but you could conceivably accomplish the end desired. Eventually.

    It really comes down to figuring out how good a job is going to be good enough, whether you want to cobble stuff together or just buy tools that make it work, or and if you have the patience to do over the course of a whole of several evenings, the amount of work someone with the right tools can do in a few minutes.

    Edit: A Youtube video showing one guy's crude but effective setup of pretty much the same thing. YouTube

    Another video showing a kinda cheesy woodworking jig that amply demonstrates an indexing method, combined with the use of a cable or chain for turning the part. YouTube
    To adapt this to a metal lathe, use a pulley diameter(the notched wheel in the video) to change the resultant pitch, and you could safely ignore the spring used on the chain, as you are not going to be using the tool sliding back and forth, the carriage will be only traveling lengthwise on the bed of the lathe.


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