Anyone machine the od of a pipe?
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    Default Anyone machine the od of a pipe?

    I have some 304 SS 3" pipe that I would like to try and true up the od. Also may polish the od. I may be 5 or 6 feet long . My lather only has a 40" bed. I have a steady rest with bearings. I was intending to machine one end and then swap ends and do the other. This is .240 wall thickness. I am concerned about chatter. Has anyone done this?

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    Sure, many have done this or similar. But there's likely stresses within the material such that after one pass, you'll still not have a round surface. And the three points of contact with a steady rest can cause their own issues, such as you winding up with a tri-lobe profile that has a constant diameter, but not cylindricity.

    Perhaps you should explain what you want to do with this tube when you're done, you may get better advice as to how to get there.

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    If you want a round object pipe can be a pretty crappy place to start.

    Sent via CNC 88HS

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    Quote Originally Posted by John F Peters View Post
    I have some 304 SS 3" pipe that I would like to try and true up the od. Also may polish the od. I may be 5 or 6 feet long . My lather only has a 40" bed. I have a steady rest with bearings. I was intending to machine one end and then swap ends and do the other. This is .240 wall thickness. I am concerned about chatter. Has anyone done this?
    Lather belongs in the bathtub.

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    Rig a follower rest to be opposite the cutter, much like a bar turner.
    That way you can use a larger radius tool, for better finish, and the rest will back up the forces.

    Doo it in one pass.

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    Quote Originally Posted by Milland View Post
    Sure, many have done this or similar. But there's likely stresses within the material such that after one pass, you'll still not have a round surface. And the three points of contact with a steady rest can cause their own issues, such as you winding up with a tri-lobe profile that has a constant diameter, but not cylindricity.

    Perhaps you should explain what you want to do with this tube when you're done, you may get better advice as to how to get there.
    Three points of contacts from the steady rest but the contact points are sliding around. So even if you force the pipe to slightly trilobular shape and cut it the end result is more round than trilobular. Although there is not much guarantees how round or oval or pentalobe or whatever you actually get..depends on the original pipe shape and stresses.

    Supporting the free end with with tailstock and nice 4" disk of baltic birch plywood might give enough support to turn the free end without distorting it from the "free state" shape.

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    Quote Originally Posted by ChipSplitter View Post
    Lather belongs in the bathtub.
    So do my feelthy lathes. But the tub is too small.



    Quatah hinch wall SS, yah do have a fair shot, compared to ignorant Chicom-made "black iron" (low-grade steel, long-since) "pipe".

    But still... how was it MADE? How well and by WHOM?

    How good is it NOW? EG: To BEGIN with...

    And why the full run in one go, rather than shorter sections, one at a time?

    IOW.. WTF is the end application intended?

    Decorative handrail or column? Potato cannon? Post for a yard lamp or CCTV security cameras? "Rough service" electrical conduit or downspout for rainwater? Driveshaft of some sort?

    "C'mon, man!"


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    '' Anyone machine the od of a pipe? ''

    Yes, many times when I've ''had to'' and fun it is not, ..............and 304 SS will only bring you extra grief.

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    Ok what I am attempting to to build a sawmill. I want to use the ss pipe for vertical slides to support the carriage. It would be a band saw type mill. I would have short pieces of pipe with bushings that would slide on this pipe. That way the carriage would be much steadier and possibly make better cuts.

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    Quote Originally Posted by John F Peters View Post
    Ok what I am attempting to to build a sawmill. I want to use the ss pipe for vertical slides to support the carriage. It would be a band saw type mill. I would have short pieces of pipe with bushings that would slide on this pipe. That way the carriage would be much steadier and possibly make better cuts.
    Wrong answer.

    Use "v" wheels to ride on the pipe, use another "v" wheel 180° from the first one.

    shim able, adjustable, etc.

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    A panel saw often runs on a pipe for perhaps .020 /.030 accuracy. likely you will make .010 or so steps trying to turn a pipe with a number of holdings and need to sand them out, a real bugger.

    Turn polishing with abrasive paper works with not making steps in the part.

    One can lay such pipe on a solid cribbing and shim it along the length to make it very straight on one side.
    The the V wheel would run very good on a side. Opposite might be spring loaded to hold tight , or allow .010 - ,015 clearance to a nylon pad..

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    Quote Originally Posted by digger doug View Post
    Wrong answer.

    Use "v" wheels to ride on the pipe, use another "v" wheel 180° from the first one.

    shim able, adjustable, etc.
    X 2 on that, .............in the OPs shoes I'd listen to Digger Doug

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    Quote Originally Posted by Limy Sami View Post
    X 2 on that, .............in the OPs shoes I'd listen to Digger Doug
    "Close"

    Wathca do is built the wheels as pairs of tandems on pivots.

    Four wheels per side. Two pivoting sets, one leading, one trailing a central pivot.

    And now you have averaged-out the variations rather well.

    Well proven approach.

    Think heavy off-road vehicles. And the suspension BEHIND the tank treads of rough ground armoured vehicles, earlier days. See WWII pre-torsion-bar for examples.

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    "Wathca do is built the wheels as pairs of tandems on pivots."

    Watcha do termite is explain how in 1959 cutting threads on a 50hp Niles lathe, jive with your Hong Kong banking, and you being in the jewelry trade, and an all around expert here, when you have not done a damn thing?
    You must be a super brain boy, Yuh or Yah?

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    Stainless steel tends to make a lousy rubbing/bearing surface, it's just easy to gall on the surface. You'd be better off selling the stainless and using more generic cast iron tube to make guides, if that's the best direction.

    Otherwise, some TGP (turned, ground, polished) bar might be good for bronze bushing use, or cold rolled steel squares with V-guide rollers (per DD), or hell, railroad ties (cleaned up with a plane) and caster wheels - almost anything will work better than the stainless tube you've got.

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    Quote Originally Posted by Milland View Post
    Stainless steel tends to make a lousy rubbing/bearing surface, it's just easy to gall on the surface. You'd be better off selling the stainless and using more generic cast iron tube to make guides, if that's the best direction.

    Otherwise, some TGP (turned, ground, polished) bar might be good for bronze bushing use, or cold rolled steel squares with V-guide rollers (per DD), or hell, railroad ties (cleaned up with a plane) and caster wheels - almost anything will work better than the stainless tube you've got.
    Yah, really. "Horses for courses."

    Thompson, for one prominent example, have built a durable bizness selling the Hell out of "the APPROPRIATE stuff" for all MANNER of guideways.

    Based off ignorant poor-boy shafting at the low end - clear out to exotic high-grade linear goods for top-end CNC.

    And they have competition. Plenty of it!

    Our OP ain't even CLOSE to "the first guy" to seek to guide sumthin'


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    Quote Originally Posted by John F Peters View Post
    Ok what I am attempting to to build a sawmill. I want to use the ss pipe for vertical slides to support the carriage. It would be a band saw type mill. I would have short pieces of pipe with bushings that would slide on this pipe. That way the carriage would be much steadier and possibly make better cuts.
    Don't do that.

    TGP or chrome/nitrided cylinder stem is the answer.

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    Not sure why I miss spelled that.

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    I thought about cylinder rod but being solid is really heavy for 3" diameter. Now I know there is hollow cylinder rod for telescoping cylinders. That would be best if I can find those.

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    Quote Originally Posted by John F Peters View Post
    Not sure why I miss spelled that.
    T - H - A - T?

    No fear. PM community generally "gets it" off of context without much noticing.

    Many among us turn spell checking off as a nuisance and are somewhat indifferent typists.

    SP is no help with one of my chronic cobbled-keyings that swaps "from" and "form", both directions, f'rinstance.



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