Distorted thinking

[DAPPH]

I've got six angle iron 50x50 x 5 mm frames to make each around 1 mtr long by 750 wide , using my old stick welder & 3.2 mm general purpose rods

The idea is to put these frames on high spec lockable castors and sit various bits of heavy mas I didn'tachinery on them so that they can be moved around a limited space work area as & when needed.

I made the first frame over a day as two "L's " tacked the corner then welded them up to make the rectangles . I did clamp them wwith some crap clamps , I don't have any decent clamps.
As i had other things to do out in my glasshouse I was leaving the welded parts to go stone cold , then coming back to do a bit more , in the end it welded up quite square & flat with less than 1/8 inch twist distortion and near perfect equal diagonals to it .

However the next two frames done a day later in the same manner over an hour or so ended up with a 20 mm twist in each . I did clamp them but didn't let them go really cool before completing the arc welds.

Question .
Besides letting the weld go completely cold each time , then clamping in position and tacking , letting it go stone cold before fully welding each joint , would it have been better as well s letting each step go stone cold to make an "L " then make it into a "U " then put the last section in clamp it to a plank of timber and weld it at both ends .

Your thoughts / advice is going to be much appreciated .
Dave

 

[Welderpaul]

Tack all 4 sides together before welding. That way the free ends are restrained. A frame like that should distort very little when it is welded.

 

[BrokenBiker]

as pauls says, take the entire thing up to begin with, then it has added rigidity when welding...

i have a few square angle iron frames to make up today if it stops raining, i will be mig welding them but same principle applies...tack it all up ( i like to get 3 tacks on each corner), then i will probably let them cool as i will tack all 6 up first ) then i will weld one flat on each corner up on all of them, then the other flat afterwards, working opposite to the last weld where possible. its worked for me in the past.

i also find it helps a lot if you can mitre cut the corners and hit them in one quick pass, a lot less welding then so less heat etc...

with my plan i am only going to need 2 welds on each corner, where as if i didnt mitre them and didnt have enough power i would have to make up to 4 welds if i wanted full strength (which i do)

 

[Arclikeharrypotter]

Agree with the above plenty of tacks!!! Keep checking for distortion as you weld!

 

[DAPPH]

Thanks Guys ,
Yes I mitred all the corners and ground them back to give a slight " Vee " .. I did tack the corners but made two "L"'s first then joined them up . I can see where I've gone wrong .
So , looks like I'll have to get a sheet of thick ply and screw it to some scaffold planks that I have to try and get a flattish table top to work upon .

 

[addjunkie]

I must confess to doing that in the past, was making a tubular frame, drew it all out on a sheet of ply, put pieces in screwed bits of wood on to hold pieces in place, then tacked it all up with the mig. Took it out and welded it up. Kept putting back to check it hadnt moved too much.

Worked ok but obviously wood and welding dont mix.

 

[Dee J]

...

Worked ok but obviously wood and welding dont mix.

Wood and weld is not to much of a problem. Working outdoors - solid top pallets make a good surface to set out and weld on. A bit of scorch, but no disaster.

 

[Kent]

Wood is not uncommonly used as tempary figures - the operative bit is tempary!

It's very rare to make a fabricated item were every component to be fused by welding is not fully tacked before its fully welded out
Yet it's one of the most common error made by the less experienced

 

[Dieselman 63]

Wood is not uncommonly used as tempary figures - the operative bit is tempary!

It's very rare to make a fabricated item were every component to be fused by welding is not fully tacked before its fully welded out
Yet it's one of the most common error made by the less experienced

I've seen flame cutting around a ply template, the edges are lined with strip so it doesn't set the thing alight. Easy to manhandle, and inexpensive if you accidentally cut the template

 

[DAPPH]

Wood is not uncommonly used as tempary figures - the operative bit is tempary!

It's very rare to make a fabricated item were every component to be fused by welding is not fully tacked before its fully welded out
Yet it's one of the most common error made by the less experienced

I bow in shame to that one Sir .

 

[Kent]

I bow in shame to that one Sir .

You won't do it again! Anyone who says they have never ever done it was hand fed too much when they learnt. Sometimes it's tempting for a verity of reasons

 

[addjunkie]

Making cock ups is a good way to fill the scrap bin, to practice ready for your next triumph. Learning is an interesting process, though wt time frustrating.

 

[DAPPH]

Wait tiil you guys read my " Trestle " thread .. then smile and offer advice .