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Thread: Need help with a machining job

  1. #1
    Join Date
    Sep 2006
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    Default Need help with a machining job

    I need to cut grooves down the center of this tube, ID is .5" Diam. Now the quick answer is "cut it like it is rifling" The quick answer is:
    1. I don't have the equipment
    2. it is wider then rifling would be so the load on the cutter might be to high to work, at least for anyway I can think of. Maybe OK for professional equipment which I don't have.

    The twist is about 1 in 30, the groove is 0.050" wide and 0.008" deep. 4 grooves spaced equally around the bore.
    I don't have any special equipment like a CNC shaper with a 4th axis rotary table etc. (don't laugh, that might actually work)

    Any ideas?

    Last edited by loose nut; 09-13-2018 at 06:27 PM.
    The shortest distance between two points is a circle of infinite diameter.

    Bluewater Model Engineering Society at https://sites.google.com/site/bluewatermes/

  2. #2
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    Nov 2007
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    Clovis CA USA
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    Default

    How must are planning spend or time for the set.
    What size of mill do you have

    Dave

    Quote Originally Posted by loose nut View Post
    I need to cut grooves down the center of this tube, ID is .5" Diam. Now the quick answer is "cut it like it is rifling" The quick answer is:
    1. I don't have the equipment
    2. it is wider then rifling would be so the load on the cutter might be to high to work, at least for anyway I can think of. Maybe OK for professional equipment which I don't have.

    The twist is about 1 in 30, the groove is 0.050" wide and 0.008" deep. 4 grooves spaced equally around the bore.
    I don't have any special equipment like a CNC shaper with a 4th axis rotary table etc. (don't laugh, that might actually work)

    Any ideas?


  3. #3
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    Default

    My quick answer would be turn it over to someone that DOES have the equipment.

    Or make it. The hardest part will be to make the helix cutter. Think broach with a pull cable or press. You do have a press, right?

  4. #4
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    Default

    interesting challenge. What sort of accuracy is required? How Rube Goldberg are you prepared to go? what machines are available?

    you've got to turn the work while moving the work axially relative to the cutter (obviously). if you need accuracy, you'll need to synchronize the feed of tool relative to work and rotation of tool relative to work as well make the four divisions.

    Perhaps work mounted in the lathe, carriage moves back toward tailstock pulling cutting through the work. As it does so, a cable connect the to carriage turns the the spindle....obviously geared or from pulling the cable off a large dia drum. Not super elegant, it gets Rube'ish (rubbish?) quickly. The other direction is in the mill some how with a electronic coupling ala John Stevenson between rotation and feed....still some challenges on what holds what
    .

  5. #5
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    Do it the old fashioned way by making your own rifling guide by rolling a log over a chalk line and chiseling a groove in the log. Then using the log on a slide to drive a tiny little scraper bit.
    *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

  6. #6
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    I'd do it on the lathe. Workpiece in the spindle, supported on the back side by a spider. Large gear on the headstock, small gear on the leadscrew or gearbox input (potentially with a compound in there too). Now, drive the lathe using a handwheel or motor on the leadscrew. Just have to figure out the gear ratio.

    As for the tool, I'd probably make something like a sliding fit boring bar, but I'd use it pulling rather than pushing. I'd probably point the toolbit out the bottom of the bar, and cut a flat area around the toolbit, so chips drop down and don't get wedged. Infeed would be by a small jacking screw behind the toolbit, perhaps on a shallow angle with a wedge behind it, and a second screw to lock it.

    allan

  7. #7
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    I visited colonial Williamsburg, Virginia many years ago. It is a living museum where they dress in 1700 1800 clothing and do things they way it was done in that time period. One of the things I never forgot was they had a device for rifling a barrel of a gun made out of wood. It was a piece of round wood with grooves in a spiral pattern that matched the rifling they wanted to produce. For the OP, something like that could be done to produce to grooves if no other equipment is available. Here is a video. The rifling starts around the 10 - 11 minute mark.

    As an aside they had sheep there with long tails. Never saw that before lol.

  8. #8
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    Louisville Ky
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    Don't know if this would fit your need or not, but this young lady shows one way to do it.

    https://www.youtube.com/channel/UCrT...MHnpWFw/videos
    Jim

  9. #9
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    [QUOTE=Mcgyver;1194859]interesting challenge. What sort of accuracy is required? How Rube Goldberg are you prepared to go? what machines are available?

    Accuracy is not critical, some amount of error is OK.

    Lathe, Bench mill.

    I have thought about the rifling method but not having done it before I would probably scrap a lot of pieces to get a good one just as someone trying to learn how to rifle a real barrel would.

    Something I forgot to mention, overall length is 10", grooved length is 8".
    The shortest distance between two points is a circle of infinite diameter.

    Bluewater Model Engineering Society at https://sites.google.com/site/bluewatermes/

  10. #10
    Join Date
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    What material is the tube?
    When I get Time... I'll...

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