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How exact of a fitup do you need

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  • How exact of a fitup do you need

    I'm getting ready for my first real project which will be a new workbench for my 9x30 metal lathe. How exact of fitup do I need with square tube. I was thinking of using 4x4 3/16 wall. It has rounded corners just like the 2x2 .25 I was originally considering. Do I need to shape the fitup or is 1/8-1/4" an exceptable gap to be filled with the bead?

  • #2
    That's quite weldable with MIG or stick...the gap will aid for strength.


    • #3
      Just make sure you tack it first on both sides. Otherwise, the first weld will pull the tube "around" the other.

      Still building my new old truck - see the progress!

      Square Wave TIG 200 - Woot!


      • #4
        if you want it to remain square, true, and plumb, don't leave any gap. Tack heavily in 4 corners quickly, and clamp it well. You don't need to 'fit' the pipes for the radius, just use a heavy fillet weld there.

        we build machine frames with similar tubing (usually 1/4"), that support hundreds of lbs of machine parts that operate at a fast speed with alot of mass changing directions. We fit the parts up on our vehicle lift, with flat plates and clamps in the corners.

        even with these parameters, we don't try and achieve full penetration with gaps in order to keep these frames less than 1/8" out of square and true over 10ft or so. we have no issues with failures, with the exception of a few caps on some pipes that were ground down too far (cosmetically needed where operators can see the frame.
        Last edited by JoeS; 02-08-2010, 08:58 AM. Reason: added some clarification