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  1. #16
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    Jul 2009
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    Melbourne
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    114

    Default

    What about a brace across the bottom between all the feet, flexing it back and supporting it ?

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  3. #17
    Join Date
    Mar 2009
    Location
    BrisVegas
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    71

    Default

    Yeah I was thinking about that, probably will add a brace/spreader at the feet just to set the correct distance while I do the curve adjustment. And a bit of force in the right direction will do wonder I'm told.

    Actually it was stood on it's end while I did the welds at the top of the legs, so it was flexing a bit under it's own weight. But that wouldn't have been enough to contribute to the curve would it? It's not that heavy, only 1.6mm wall tube.

    I haven't had a crack at this yet, figured I'd better do any cleaning up (grinding) first in case I need to re-weld anything.

  4. #18
    Join Date
    May 2008
    Location
    Perth
    Posts
    164

    Default

    Only 1.6 wall?
    Based off my experience, at the risk of being to the ire of the older hands, I'd say you're way, way overthinking it
    Reshape it with a bit of the old gentle persuasion tool, aka a hammer.
    Or, see if the surface will have enough weight to push out the bulge. That's one of the nice things about thin walled tube, much more responsive to a friendly beathing than its thicker skinned brethren.

    Having worked on it on its side will have worked against you, once again only my experience which I'm willing to admit is relatively brief, I've found that bracing things into their desired positions tends to set them there, so once you release the brace/clamp/etc, it doesn't shift unwantedly. But in your situation, going over the top would create more headaches than it'd fix.

  5. #19
    Join Date
    Jul 2013
    Location
    nsw
    Posts
    118

    Default ratchet straps

    I've used ratchet straps to bring things into line from time to time.

    to level up your frame, perhaps strap the two middle sections down and with some heat (or cold ) you could ratchet the two outer frame sections upwards.

    i usually use my truck bed to ratchet down and then use an overhead beam or tree : ) to ratchet upwards.

    for heat straightening - heat the top of the rainbow so that on contraction (cooling) the rainbow straightens : )

    just my 2 c worth

    cheers

  6. #20
    Join Date
    Oct 2011
    Location
    Adelaide
    Age
    59
    Posts
    3,149

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    Are you sure what you are seeing is not just straight sag? From the pictures it looks like one end is hanging without any support and that will tend to distort things. You really need to have it on a flat floor before doing things to 'correct distortion'

    Michael

  7. #21
    Join Date
    Feb 2010
    Location
    Ballina, NSW
    Posts
    725

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    The challenge is to find something flat and immobile to lever against. One option you may not have thought of is to pin down the middle of the frame by using lengths of wood extending down from the ceiling joists and then either manually levering or otherwise jacking up (car jack, ratchet straps from ceiling joists, etc.) the ends of the frame to the required degree of flatness. Once you flatten out the horizontal bars then it may turn out that your end legs are splayed out too far - in which case I would get a cut off disk to cut halfway through the offending welds, clamp thoroughly at the correct angle (maybe even pre-compensate a bit for distortion), then reweld those bits.
    Cheers
    - Mick

  8. #22
    Join Date
    Jan 2004
    Location
    Mackay Qld
    Posts
    3,466

    Default

    Hi just some comment on the black painted practice RHS. It is meant as constructive criticism so do not take offense.

    I draw attention to the fillet break of the welding in the orange box. The result is not good at all.

    There has been little or no fusion there mostly because of the incorrect setting and also because of the lack of preparation -no paint removal.
    if the weld setting of the weld in the blue box is the same -the LOF will be similar to that of the weld in the orange box.

    There are two controls. One each for adjusting the wire feed and the voltage. The wire feed which is the equivalent to amperage increases as the metres per minute rate of the wire speed is increased.

    The voltage control affects bead profile. The supplied photos indicate that the voltage is way too cold. The weave is excessive.bead width as someone mention is relative to material thickness.For example a RHS wall thickness of say 2.4 would be well served by a bead leg length(measure vertically and horizontally) of 3mm. I estimate bead width to be close to 12mm.< edit> Also consider lifting the torch angle to get the angle of the wire pointing into the base horizontal metal.

    Lastly, cleaning all material that is not intended to be fused is mandatory.Paint,grease,oil rust ,dirt can contain material that will be harmful to the weld in its molten condition. A shiny clean metal condition is always best.

    May I suggest you go here to get a better idea of setting your mig.

    http://www.millerwelds.com/resources...elding-basics/


    cheers

    Grahame
    Attached Images Attached Images

  9. #23
    Join Date
    Mar 2009
    Location
    BrisVegas
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    Thanks Grahame, all help is appreciated.

    The weld you highlight in the orange box - yes that was a definite failure, one of the very early attempts/tests. The weld in the blue box was done using very different settings indeed. All the steel used there is actually painted RHS, I've used a flap disc to remove the paint so, it's shiny as anything but probably looks black because of the poor lighting.

    I have been wondering about the wire size I'm using, but kind of pushed that out of mind because I seem to be making pieces stick together. It's 0.9mm wire, the steel I'm using is 1.6mm wall. Going by the Miller website you mentioned, I should be using something around 0.76mm wire (0.8mm)? I asked this question to a friend who has done welding (commercially) in the past, he seemed to think that there wasn't much difference between 0.8 and 0.9mm wire?

    Although I'd never thought about wire size as setting the amperage, I thought that had more to do with the torch distance to/from the workpiece. So that's good to know.

    But I'm still a bit unsure how wide the weld should be for this material thickness? It seems like the voltage needed requires a wire feed speed that will add such an amount of metal that a small 3mm weld fillet wouldn't be possible?

    I will go back and try some different settings, thanks for the tips.

    The reason I settled on those settings was because it seemed like anything higher would blow holes too easily, and anything lower just wouldn't fuse. But maybe I will discover something when I adjust settings this time. After all, I have probably increased my experience by 400% over the last two weeks (being that this is all so new to me).

    I won't freak out about the welds I've done on the bench frame just yet, it all seems to be "strong enough" for what I want. But I definitely want to aim to do it right, and to know the correct way to do things in the future so thank you for your interest and taking the time to share your knowledge.



    And I haven't got around to fixing my bend/warping problem yet, I haven't forgotten about everyone who added comments about that - I will get to your comments soon!

  10. #24
    Join Date
    Oct 2011
    Location
    Adelaide
    Age
    59
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    3,149

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    Quote Originally Posted by mugget View Post
    But I'm still a bit unsure how wide the weld should be for this material thickness? It seems like the voltage needed requires a wire feed speed that will add such an amount of metal that a small 3mm weld fillet wouldn't be possible?
    I think the point that Grahame was trying to make was that the fillet was too large. 3mm may well be too hard to do (at least for the moment), but you should be aiming for a filllet smaller than the one shown on the tube. If you think about the material thickness in the throat of the weld, ideally this thickness should be at least the thickness of the material being welded but preferably not much more. In reality no one will care if your weld leg length on a job like this is say 6mm but people who are serious about their welding recognise that small neat welds take more skill, cause less distortion and so are preferable to the enormous blobby things that most of us make when we first start welding.

    I used to think welding was something that did not take much skill but after working and watching some highly skilled welders and trying to produce decent looking welds myself I now have the view that it is a skill that verges on an art form. Some people are happy if the material just sticks together and stop there but really it can be taken as a continuous challenge to improve your skills and technique if you wish to go that way.

    Keep practicing, keep trying things to get results that you are happy with.

    Michael

  11. #25
    Join Date
    Jan 2004
    Location
    Mackay Qld
    Posts
    3,466

    Default

    Quote Originally Posted by mugget View Post
    Thanks Grahame, all help is appreciated.

    The weld you highlight in the orange box - yes that was a definite failure, one of the very early attempts/tests. The weld in the blue box was done using very different settings indeed. All the steel used there is actually painted RHS, I've used a flap disc to remove the paint so, it's shiny as anything but probably looks black because of the poor lighting.

    I have been wondering about the wire size I'm using, but kind of pushed that out of mind because I seem to be making pieces stick together. It's 0.9mm wire, the steel I'm using is 1.6mm wall. Going by the Miller website you mentioned, I should be using something around 0.76mm wire (0.8mm)? I asked this question to a friend who has done welding (commercially) in the past, he seemed to think that there wasn't much difference between 0.8 and 0.9mm wire?
    with smaller diameter wire,it will take a greater arc density( read more arc energy) due to the smaller diameter

    Although I'd never thought about wire size as setting the amperage, I thought that had more to do with the torch distance to/from the workpiece. So that's good to know. The greater the wire stick out ,the less heat in- it has a limit as you can lose gas cover if you come back too far- conversely get in close and you get better peno

    But I'm still a bit unsure how wide the weld should be for this material thickness? It seems like the voltage needed requires a wire feed speed that will add such an amount of metal that a small 3mm weld fillet wouldn't be possible? Travel speed plays a part here-also I wonder - are you pushing the wire - not dragging it?

    I will go back and try some different settings, thanks for the tips.

    The reason I settled on those settings was because it seemed like anything higher would blow holes too easily, and anything lower just wouldn't fuse. But maybe I will discover something when I adjust settings this time. After all, I have probably increased my experience by 400% over the last two weeks (being that this is all so new to me).

    I won't freak out about the welds I've done on the bench frame just yet, it all seems to be "strong enough" for what I want. But I definitely want to aim to do it right, and to know the correct way to do things in the future so thank you for your interest and taking the time to share your knowledge.



    And I haven't got around to fixing my bend/warping problem yet, I haven't forgotten about everyone who added comments about that - I will get to your comments soon!
    Warping or distortion is usually because of too much weld.Most people over weld. I have a SHS bench that has held together for near 25 years and only welded with about 20 x 12mm tacks. If its a bench, the load on it will never be that great.Its been moved once and the movers stuck our household goods on and under with no movement of deflection at all.
    We can go into the distortion and its control, side of it, later.

    Grahame

  12. #26
    Join Date
    Jan 2004
    Location
    Mackay Qld
    Posts
    3,466

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    Mugget,

    The following won't help much for repairing the warping to date but will assist greatly in preventing future problems.

    Further to the comment on warping - it's called distortion in the industry. Distortion is present in some degree in all welded work, the trick for the welding operator is being able to control and manage it.

    One of the direct causes of distortion is over welding. Not only the weld bead being too wide what but also there being far too much linear deposition .

    Fully welding something instead of laying down a series of short welds is one of the culprits. RHS tube with thin wall is purchased principally because of price per metre with thought not often given to the weldability and resistance to distortion(warping )

    If I had to hazard a guess I would say 90% of home fabrication welding is over welded.

    I have told you all that so i can tell you about the following, a U tube video originally produced as a war industries training film by Disney studios to assist in the WW2 training of welders, most who had no prior experience. Be prepared as the mixed film and animation are presented in the language and context of the time, ie it sounds really old fashioned.

    The message however remains the the same for todays welding applications - nothing is changed. This movie has trained legions of welders for 70 odd years.

    This is what welders are taught.

    https://www.youtube.com/watch?v=2vuGlcbDwKY

    I hope you enjoy it.

    Grahame

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