Thread: Joint strength

hi Lyle ,
The shear strength of the a glue bond will be way below that of a welded fusion joint.
In a properly welded and configured joint 25 mm of 3.25 bead will hold the weight of the average family sedan-say around a ton or therabouts.

Where it all hits the fan is in in the quaity of the welded bead, joint design and how it is laid down.

Most welding down in the DIY is mostly overkill resulting in wasted materials and distortion and waste of time grinding it all back for cosmetics.
see illustrations below.
More than anything it is making the job fit for its purpose.Theres little point in making a bulldozer type strength structure,if you only need a garden gate.
In most RHS box section joints the problem will be in too much peno as people buy it by price and end up with only 1.6mm wall thickness to weld into. Thers quite a few posts on that subject here if you want to do a search.


Grahame

Thanks Grahame. I understand what you have said, now to apply it.
I am practicing like crazy to get to know my machine and improve the weld. My welding training is very old. I did a TAFE course many years ago. So this is bringing back a lot of memories.
I have destroyed a few joints to see the penetration. Not too bad, nothing pretty. A bit "McGiverish".

I think I'll just do butt joints not 45 degree angles. Much easier and less room for error on my part.

Thanks again Grahame.

Lyle.

45 degree joins can also be a bit of a mixed blessing - the long join top and bottom will want to close up as you weld along it, pulling the two pieces out of square, thus you need to be particularly careful about your tacking.

The same issue of expansion and contraction obviously applies to butt joins, but tends not to be so severe.