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  1. #1
    blake in spokane is offline Hot Rolled
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    Default Cutting Angles On Tubing

    Is there a forumla to figure a "bird's beak" type miter to weld tubing at different angles like on a race cars roll cage? In this case I'm working with 1-1/4, 1-1/2, & 2"

  2. #2
    mf205i is offline Cast Iron
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  3. #3
    winchman is offline Stainless
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    Most people use something called a Joint Jigger to cut the pieces to fit. You can also do it in a lathe or on a milling machine with the proper attachments.

    Using a pattern to cut the end can lead to lots of grinding or filing to get a good fit on thick-walled tube. The other methods are quicker and give better results. The cutting patterns are good for sheet metal ductwork, though.

    Roger

  4. #4
    Mike C. is offline Diamond
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    My preference is a shell mill in a swivel vise set up on my Van Norman in horizontal configuration. The radius doe not have to be super exact for good results.. ie, a 2 1/4" diam mill wil fit tubing from about 1 3/4"-2 3/4 with almost no slack.

  5. #5
    bjorn toulouse's Avatar
    bjorn toulouse is offline Titanium
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    I have good results using an end mill, the size of the tubing OD, with my vertical mill. I TIG weld my joints, so close fit is required.
    Annular cutters work well also.


    Rex

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    I agree with Winchman, Mike and Bjorn above.

    If you don't have a small milling machine, (if you do, strike this part), medium machines are cheaper and more useful.

    In your case, the purchase of 3 sizes of milling cutters and you'd be set.




    Temporary set-ups are easy but if I did this more frequently, I'd build an adjustable fixture that would cover all the angles and size ranges that I needed. By that I mean, V-block type "jaws" that would easily accommodate all diameters.

    That's 2" water pipe, about 2-1/4" diameter.

    Bob

  7. #7
    Clive603 is offline Titanium
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    For up to 2" and perhaps a bit bigger a steelworkers Magmount drill running rotabroach cutters makes a reasonable substitute for a a milling machine. Magmount it to a suitable lump of I section steel beam and bolt angled holders on as required. More agricultural than a proper machine but its easy to weld up holders as required and there are no worries about drilling bolt holes to fixture things. The one I saw, at a stainless steel tube fabricators, had left and right hand holders on a single fixture to do both sides of the tube. Obviously side one had a locator matched to the square end whilst side two picked up on the half done beak. I imagine you could do it on a single holder with a de-mountable pin to make the second cut exactly 180 to the first.

    Clive

  8. #8
    ecortech is offline Aluminum
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    Think this may be what you are looking for Tools for Coping Angle

    Also check out http://snip.awardspace.com/ just input your values and it calculates the needed angles to cut.

    Ed

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    Thank you Ed for the links, especially the calculator, I'll save my mills for better stuff.

    Bob

  10. #10
    blake in spokane is offline Hot Rolled
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    Thanks Ed, Thats the post I'm looking for. Like the other guys I used milling cutters, holesaws, & lots of $.

  11. #11
    CalG is offline Titanium
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    Just in example of options:

    I worked in an outfit that made specialty aviation seating products. We found that profiling the many pieces of 4130 tubing used to produce a finished seat frame on machine tools with cutters, time consuming and troublesome.
    Switching to mylar "patterns" that were transfered to the ends of cut to length tubing by pencil line and subsequently GROUND, off-hand on a simple bench grinder fitted with wheels dressed to the required radius. The wheels thickness was choosen to suit the tubing diameter as well. We only used two tube diameters, so the bench grinder had a wheel of each width fitted to the two ends.
    A certain learning curve was to be aquired by the grindhand to best match the fitting angle of the tubing, but that was not much of a problem. One or two practice efforts on a cut off was usually fine. The fit was usually very good indeed. High quality welds were easily obtained.

    Without cutting oils, the reduced pre tig weld clean up, along with the ease of deburr and chamfer were time savers too.

    We made many hundreds of these assemblies and I still suggest the method, though soft or thick walled material may better match the milling process.

    Oh! the patterns produced with these "free ware" applications have worked just fine for recent projects. some "fudging" of first part expected.

    Regards

    CalG

  12. #12
    Peter. is offline Hot Rolled
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  13. #13
    awake's Avatar
    awake is offline Stainless
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    As I recall, the promo video for the KMG belt grinders shows how you can use different size rollers to grind perfect radii. Anybody do it that way?

  14. #14
    wment is offline Aluminum
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    Check out this notcher.
    http://www.lowbucktools.com/notcher.html
    It is not as precise as some of the methods mentioned above but is quick and works quite well. For 90 deg miters use one bite per side. For other angles more bites can be taken off one side that the other. It is a very handy tool.

    wm

  15. #15
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    Motomoron is offline Hot Rolled
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    It took me a couple minutes to find this, but here it goes:

    http://www.pirate4x4.com/tech/billavista/Links/

    ...There's a whole lot about rock crawler suspension design and fabrication, which is interesting enough, and a slick way to cut fishmouths with a chop saw.

    I truly believe with a chop saw and a big enough MIG welder you can move the earth.

    I've tried this chop saw and bench grinder deal, and while I wouldn't build a roll cage for my car this way, it's close enough for less rigorous tasks.

  16. #16
    Mud's Avatar
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    Mud is offline Diamond
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    Quote Originally Posted by awake View Post
    As I recall, the promo video for the KMG belt grinders shows how you can use different size rollers to grind perfect radii. Anybody do it that way?

    I've seen it done at trade shows. Lotsa sparks and dirt of course, and leaves a nasty flash that needs to be ground off. Makes it pretty hot too. I think an endmill is just as fast, but it requires a larger investment if you don't already have a mill or lathe handy.

  17. #17
    Bssc is offline Aluminum
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    Search out tubing mitering on google, there are many ways to accomplish the task. I do thin wall cromo , Ti and CF with a file and a china marker.

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