[reidy01]

G'day all, I was wondering if say welding mild steel 2inch x 2inch box section to make a rectangle type frame, what would be stronger for the corners a miter joint
or cut it straight and butt it together and weld? I'm thinking the butt option right?

[Otto Nobedder]

Miter joint has more welded area. Whether it matters depends on how the weld is loaded.

Gut reaction, unless you're building a car frame, do what you're comfortable with.

Steve S

[reidy01]

Hey Steve thanks for getting back to me so quick, it's for a trailer. So it will be loaded with some stuff for camping and the like. So it will have some twisting forces going over things and stuff like that.

[Otto Nobedder]

I doubt there's any justification for the extra work of mitering it.

I'd cap any open ends, though, and treat them on the inside. Pour 'em full of oil or paint, and pour it back out before welding caps. Keeps the tubes from "rotting" from the inside.

Steve S

[reidy01]

Yeah that's what I thought, but wasn't sure which one was stronger. Thanks Steve. oh and thanks for the tip with the oil/paint.

[Alexa]

Reidy01.

Consider the importance of beveling the pieces and welding them with full penetration, resulting in the weld through thickness being at least the same size of the wall thickness.

Alexa

[TamJeff]

If you frame anything that moves on a roadway, and when in doubt, the engineering needs to go further than just weld joinery. Consider gusseting as another structural option. Plus they generally look cool and add a more engineered/finished look to projects.

[Otto Nobedder]

Good point, Jeff.

I was focused on the specific question, and the gusseting is a great add. However, it may be redundant, depending on how the trailer is decked. A welded deck, even one of expanded metal, or even glue/screw plywood will turn the entire top surface into a shear-web, making gussets unneccesary.

In reference to the drawing you posted, that is a flawed design. When a gusset is required, it should be flush with the top or bottom (or both) of the square/rectangular tube, not the center, unless "doublers" are used to tie the gussets to the top and bottom webs.

Steve S

[TamJeff]

It was just the first image I came across that wasn't a bolt-on made of stamped steel. I'm not particularly fond of google's newest image format so I tend to be a little lazy with it. Most gussets/braces I use end up being made of the tubing itself to keep from becoming a debris or contaminant trap. I agree completely with your opinion, though.