I have a spare length of box section and I am making a barbell

Depends. Do you plan to weld it together, glue it together, tape it together or string it together with bailing wire? Do you have competency in any of the above? Geez, can you read the sticky you dummy.

>>1022719
>I am making a barbell stand like pic related.

You can clearly see where it's welded and where it's been bolted together.

I'd say it's not the metal that will come into question although most barbell stands use 60/40x5mm. It's down to how well your welds will hold.

>>1022704
Loaded in pure compression, two short tubular columns of that size would be able to hold about 25 tons before yielding. In a barbell rack like that, load limits are based on more difficult loading, like lateral forces (the frame is stressed in weaker directions) and impact forces (a 1kg weight can easily produce brief loads of thousands of Newtons). Weld it competently, triangulate all connections, and it should be strong enough for anything you can lift.

>>1022704
That rack could hold up a goddamned car. The weak point is the pins that allow height adjustment. Makes sure the pins are strong enough not to shear under impact forces from a few hundred pounds. Anything grade 5 should be fine, buy grade 8 if you're really worried.

Even if the rest of the stand is put together in a half-assed way, those pins will still be the weak point.

>>1023881
Or make it non-adjustable and set at the height you want. Less work and more strength but less versatility. If you do use pins, use ones bigger than in the image.

Shit. You lot are retarded. If the kid cant weld, pins wont be sheared by fuck all. More like kid tries to rack a few kg without a spotter and has lateral forces from wobbling under the 30kg load, resulting in the cross member falling the fuck off as he cant weld. Not even considering that gal is more nasty to weld than normal.

In short : if you can weld, your fine. use 12mm or larger diameter bar for pins, at least 100mm long with a bend in them. Should be fine for more than you can lift, however ensure you have stablisation (ie adjustable feet (12x1.75 hex bolts into nuts welded into the four corners)) so it wont rock and is stable af.

Cant weld - go buy one for $50

Cant weld and weld anyway - get a friend from /b/ to take pics for rekt thread. I promise to save.

Material strength will be good, fail point will be based on construction.

When you do build this, strap every weight you have on it, then paint cans, jugs of water, fat pets, then lean on it and shake it.
If it's still standing then you might be alright

>>1026137
Or just slam the weights on it from above and keep your feet out of the way.

Also google home built gym equipment. To succeed, copy success.