novice needs advice!!!!!

[johnhooper]

feel really stupid asking this, I need to make some box section frames (20mmX20mm mild steel) with my mig. I can produce a fairly tidy weld no problem, but am struggling to maintain a 90 degree angle at the joints and the whole thing ends up banana shape despite being clamped to a heavy steel table, HHHHHEEEEEELLLLLPPPPPPPPPPP!!!!!!!!!!!!!!! Its driving me mad!

 

[fingers99]

You need to tack weld it all round then do the final (continuous) welds. With the odd tack on one side you can generally straighten it out (ready for the opposite tack) with a whap from a hammer/rubber mallet (or two).

 

[shenion]

Lots of tacks.

I saw someone demonstrate when welding box section that going from the outside-in on the diagonals reduces the amount of distortion. Have not tried it yet

 

[runnach]

When making up square or rectangle frames I make them up into fully welded L's first, once cool square them up, then put them together and fully weld till frame is complete, check diagonals to check for square, dunt appropriate corner of the floor/bench to bring back to square.

I find this best method for making up frames, 20x20 will be a dawdle.

Cheers............

 

[johnhooper]

thanks for your help, i guess that the shrinking that occurs when the steel cools is causing the warp?

 

[shenion]

Yes, especially if there is any gaps.

 

[johnhooper]

yeah, that makes sense. I will have to check that my chop saw is cutting nice and square!

 

[johnhooper]

thanks for the advice, i discovered that my heavy steel table is banana shape!! did them on a flat thick plywood and they came out great