Hi,

I am not an engineer but trying to understand bolt strgth, tensile
strength og steel and some other varribles for something I am wanting
to construct. I am wanting to build a car dolly and/or dual axle
trailer. I have welders and have welded on hobby projects but by no
means consider myself an expert welder. My idea is to both weld and
bolt a square togther to form the frame. I have some 3 inch square
tubing laying around, I believe is is 1/8 thick but not sure. It came
from some material stand at work that got cut up.


My idea was to get some scrap 1/8 inch plate and torch cut two “L”
brackets and weld them togther to form a ¼ inch L bracket. These
would
go on all 4 corners of the square I would bolt each L with bolts
through the L and through the 3 inch tubing. Before doing this I
would
insert a section of black pipe through all pieces for the bolt to
ride
in. After bolting and everything being square I would weld all joints
with 6011 or 6013 rod with either my AC buzzbox or the mIller
generator welder I just aquired on DC. (Not welded with it much yet)
(I have trouble welding with 7018 for some reason.


My question becomes, what size bolts would be adequate? I get
confused
when I see specs on bolts such as shear strength, tensile strength,
yield strength, etc? I suspect the bolt need only be as strong as the
streth of the bolt steel around it. I am having trouble finding the
specs for mild steel strength but think it might be around 38,000
PSI?
Is this true?


Any help is appreciated!