can not square a job

[Madmc]

Hi there

I'm busy welding right ange post and cannot get it square. Its 114d 4mm wall and it wasnt mitred right so the inside gap was about 6mm at 90 degrees. The post is 2700 H X 700 W so I've got a 200mm guset plate wedged in for strength. I've tried tried cross tacking a bit of 4x2 channel across so it doesnt move but when I cut it off it moves. Its really annoying and I'm sure theres an easy way of know the correct amout over 90deg to tack it at or another trick to get it right.

Any advice would be greatly appreciated!

Regards

madmc

 

[Welderpaul]

Easiest way to get them square is to lay the tubes on a flat surface, butt the two mitres together at 90 degrees (using a square) until they touch (at the outer corner in your case if the mitre is wonky).
Check the two leg lengths are correct.
Pull the legs inwards slightly so it is marginally under 90 degrees and place a decent tack on the outside of the joint on the centre line of the tube.
Check the joint for square and push the legs outwards until they are exact. Place a tack on the inside of the joint, again on the mid point of the tube. Check again and it should be fairly accurate. Tack the gusset plate in and then weld up.
Tacking a brace or 'sprag' across the legs before welding up will help stop them pulling. Sometimes handy to weld it up set slightly over 90 degrees so when it inevitably pulls in a bit it will be nearer a right angle.
A gert gap to fill on the inside of the joint will mean it will pull more than normal owing to the extra weld and therefore heat you will be putting into it.

 

[Delgado]

To add to Paul's already sound advice, whenever you weld a 90 degree angle (be it box, angle or tube) always weld from the inside corner to the outside, flip it over and repeat.

After a while you'll learn how much it's likely to move, and the way I've described, if anything, will make it open rather than close up (which you can allow for). Also, after something's welded it's always easier to close up an angle that's too open, rather than open an angle that's too closed (if that makes any sense?).

 

[Hitch]

The bad fitup will be your enemy, big gaps always seem to make things pull about.
I expect your chs is bending very slightly at the point the gusset ends.

Is tacking up the problem, or the welds pulling it out of square?

Cant add anything else on top of what Paul has already said.

 

[Uniqueusername]

Tack the sides, weld the outside, weld the inside.
The bad mitres will be a PITA, but basic rule is that the inside will always pull a lot more than the outside, especially when it's a bad fitup and that's usually enough to overcome the outside weld.
Bit of educated guesstimation and you'll get a feel for it. All else fails a good "donk" usually sorts it out...........

 

[Madmc]

Thanks for all the advice its all sound!