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difference between wall mild steel tubing and wallDom tubing

Discussion in 'Early CJ5 and CJ6 Tech' started by 52m38a1, May 19, 2004.

  1. May 19, 2004
    52m38a1

    52m38a1 New Member

    Jacksonville, Al.
    Joined:
    Nov 23, 2003
    Messages:
    38
    jus wondering wich is better and stronger ?
     
  2. May 20, 2004
    oldjeep

    oldjeep Sisyphus at work

    Victoria, MN
    Joined:
    Sep 19, 2003
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    267
    DOM is stronger than HREW tubing, and generally twice the price.
     
  3. May 22, 2004
    double R

    double R Member

    Reseda, CA
    Joined:
    Mar 18, 2003
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    332
    just an fyi, i think they're just called mild steel tubing and DOM tubing...without the word "wall" in front of them...you've probably seen them written like this----> 1.5" OD x .25" wall DOM tubing...that means that the metal's thickness or the "wall" thickness of the tube is .25"

    oldjeep, what's hrew?
     
  4. May 22, 2004
    oldjeep

    oldjeep Sisyphus at work

    Victoria, MN
    Joined:
    Sep 19, 2003
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    267
    From: http://www.pirate4x4.com/tech/billavista/PR-BV60/index1a.html

    Electric Resistance Welded (ERW) Tube
    ERW is the most economical and readily available type of mechanical tuning. It is produced by taking a flat bar of steel and rolling it into a tube shape (picture rolling up a newspaper - but without any overlap) and then welding the seam - by, you guessed it - electric resistance - hence the name. Electric resistance welding is somewhat like a long, continuous spot weld. It's often computer controlled and extremely consistent. ERW is normally SAE 1010 (for wall thickness < 16 ga) or SAE 1020. ERW tube comes in 2 flavours:

    Hot Rolled ERW (HREW)
    HREW is rolled into a tube at elevated temperatures, usually way above room temperature. This produces a tubing that is more malleable and therefore easier to form but that is also not as strong, is supplied covered with scale, and not as uniform in dimension as cold rolled. It is also quite a bit cheaper than cold rolled.

    Cold Rolled ERW (CREW)
    CREW is manufactured by a process in which a steel bar is rolled into a tube and the seam welded, usually at room temperature. Compared to hot rolled, CREW is stronger - (greater yield strength) - because of the improvement in the crystal lattice structure from improved grain size, shape, and orientation imparted by being worked at cold (room) temperatures), straighter, has a much smoother and more uniform surface finish, and is made to much tighter, more consistent dimensions. It is the best economical choice for tube work, and because of the better surface finish and tighter dimensional tolerances it is much nicer to work with than HREW.

    Drawn Over Mandrel (DOM)
    Strong and well-finished DOM is an electric resistance welded tube tested for soundness of weld and drawn through a die and over a mandrel. This process imparts significantly improved mechanical properties to the tube, due to the cold working process. It is considered a high quality tube, and is normally constructed from SAE 1020 or 1026 steel. Note that, technically DOM refers to the process by which the tube is finished after having started as an ERW tube. Technically, DOM is not a type of steel tube, but rather a process. As so often happen though - in common use the term has become accepted to mean a specific type of tubing rather than a process. In this case, when people say "DOM" they normally mean an ERW tube drawn over a mandrel at (close to) room temperature and made from SAE 1020 steel. It is normally drawn to O.D. and I.D. dimensions. Here is what the Steel Tube Institute of North America has to say about DOM:

    The DOM Manufacturing Process

    The manufacturing process for DOM tubing begins with coils of steel, which are slit to the proper width for the desired tube size. The strip is cold formed and passed through an electric resistance welder which joins the edges together, under pressure, to complete the tubular shape. After testing the weld's integrity, the tubing is cut to length for further processing.

    The cold-drawing process creates a uniform, precision product with substantially improved tolerances, surface finish and tensile strength, increased hardness and good machinability. In this process, the tube is cleaned and annealed, and one end of each length is squeezed to a point so it can be gripped by the drawing mechanism. The tube is then drawn through one or more dies and over mandrels. This reduces the diameter of the tube and thins its walls to the required dimensions in a controlled fashion to provide the qualities desired in the finished product. Metallurgically, drawing improves the tube's concentricity, tensile strength, hardness and machinability. Close dimensional accuracy is achieved through tight control of both outside and inside diameters.[10]
     
  5. May 22, 2004
    firegod33

    firegod33 Member

    Grand Junction, CO
    Joined:
    Jul 7, 2003
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    154
    ... or more. Often three times as much, or more.
    BTW, that's probably the most intelligent thing ever posted on Pirate.
     
  6. May 23, 2004
    80cj

    80cj Member

    Hawaii
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    Sep 1, 2003
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    554
    So I would guess that chrome moly tubing is actually DOM with the only difference being the tensile strength of the material?
     
  7. May 23, 2004
    Ledge

    Ledge Member

    Old Town, Maine
    Joined:
    May 5, 2004
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    72
    Pirate has some good info on it, the only problem is there are tens of thousands of testosterone soaked dipsticks with bad attitudes. I consult Billavista's collection of info there often.
     
  8. May 23, 2004
    firegod33

    firegod33 Member

    Grand Junction, CO
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    Billavista is one of the few on Pirate that I pay attention to. He has very good, accurate information. He also has a willingness to share that information, without calling anyone an idiot for not knowing it already.
    Chromoly is a different animal. It has nothing to do with DOM/HREW, etc... It has to do with the alloy used in its manufacturing. Chromoly costs even more and is much harder to work with than mild DOM.
    The only reason to use Chromoly is if you are building a high speed vehicle and need to save weight.
     
  9. May 25, 2004
    BESRK

    BESRK New Member

    Newport News, VA
    Joined:
    Oct 19, 2002
    Messages:
    17
    Not sure if this link could help anyone but I've used them for small quantities of metal. I used their 1 1/4" x 1 3/8" wall DOM for making tie rods. I just drill the end for 11/16" and tap it with a 3/4" die for my rod ends. It's tough stuff.. http://www.onlinemetals.com/how.cfm
     
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