As part of that lot of steel stock that I bought recently, there was a
big bundle of "structural tube", which is steel tubing 2-6 inches
diameter, with walls 1/2 to 1 inch thick.
I hae to admit that I have neer seen them used anywhere, other than in
airports. What are their uses, exactly?
My second question is, if I want to weld a tube to a plate, do I need
to bevel the tube for a proper joint?
I've made lathe spindle adapters and custom automotive tools from
solid stock that big, and wished I had thick-walled tubing instead of
hydraulic cylinder rod cut-offs to start from. The extended mast I
made for my truck bed crane is a piece of heavy tubing.
The Bailey paper catalog here shows DOM tubing to make hydraulic
cylinders with walls as thick as 1/2", though most of theirs is
You could weld two test coupons in a tee and bandsaw through the weld
to see how deeply it penetrated.
I've used lots of it in custom farm equipment.
Lots of it used in industry to mount heavy manufacturing components.
For example, mount an industrial robot upside down over an assembly
You can make a great jib crane with it. Or anything else where you
need a lot of force.
I grind to 1/8" remaning when i need to weld for high force area. Then
use 7011 rod and several passes. Then the weld is stronger than the
On Sun, 03 Feb 2013 10:19:47 -0600, Ignoramus19840 wrote:
I'm not a mechanical or a structural engineer, but I am an engineer that
designs stuff. So I can tell you with 100% assurance, that the answer is
If you're welding a plate onto the bottom of the tube to act as a footing
where the tube-plate joint is absolutely guaranteed to be in compression,
then you only need to make the weld strong enough to keep the tube from
slipping sideways off of the plate.
If you're welding the plate onto the end of the tube, then bolting the
assembly in someplace where the tube is being stressed in tension to a
significant fraction of its ultimate strength, then you need to make the
weld really honkin' strong, probably with at least as much weld as there
is metal in the tube.
If you're going to have the tube horizontal and you don't want much
deflection, and it's really long (i.e, twenty feet long or some such),
then you'd be loading the joint in shear, and with much less force than
the "tension" case. In that case, you probably wouldn't need much of a
weld to hold to the point where the tube starts to permanently deform,
although you may want as much weld as there is tube wall so that if
someone does go and try to load the thing too much it'll all buckle in a
controlled way instead of tearing apart.
You have to think about this stuff if you're an engineer, because if you
over-specify 1000 joints then it can cost a whole bunch of unnecessary
money in the welding (even more if you call out matching X-ray
inspection). If you're not an engineer and you're making a one-off and
you have any questions, I'd suggest you just make sure that your weld is
at least as thick as the tube wall (and make sure your plate is that
thick, too). You'll spend a lot more on welding, but it'll be a lot less
likely to break unexpectedly under normal loads, or inconveniently under
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
On Sun, 03 Feb 2013 10:19:47 -0600, Ignoramus19840
Angle grinder, plasma cutter or a quick pass through a lathe.
Id probably use a lathe simply because I have one big enough between
centers and swing. And its Fast.
And remember...1/16"- 1/8" separation before hot passing with 6010
On Sun, 03 Feb 2013 10:19:47 -0600, Ignoramus19840
Lots of places - For starters, any "Lally Columns" in the middle of
your basement to hold up the house above you are going to be in the
mid-range 1/2" wall range or thicker, with some matching serious beam
I could use a few chunks of it for replacement fence posts holding up
the gate hinges - Make the car bounce off rather than bend the post.
In Chicago, the same thing for building a Snow Plow Proof mailbox post
and arm assembly. Especially useful if you've got a renegade plow
driver trying to snick the wood ones off on purpose as a sport...
Paint it wood brown so they can't tell, and you can hear the
"CRUNCH-PTANG!" and "SCREECH!" of the plow spinning the truck around
before snapping off instead...
They cheat and use Sched-40 Pipe and fill Crash Posts with concrete -
but if you're dead serious about stopping a car before it hits
something - like in front of a 2500 Gallon Propane Tank - that
structural tube will do it if you plant it in enough footing concrete.
Depends on how the forces load it - but for ultimate strength yes.
--<< Bruce >>--
On 2013-02-06, Bruce L. Bergman (munged human readable)
Bruce, I was thinking about the same thing, to make a mailbox post
from this tubing.
I believe this to be against the law, if I recall correctly, the
mailbox posts are required to be not too strong and to collapse in a
collision with a car, to save the driver. This actually makes sense to
me. That driver may be someone's or my own inexperienced kid who is
skidding on ice.
I had my own "snowplow and idiot driver problem". My solution was to
build a mailbox that a) is highly visible and b) swivels away when
hit. Actually since I made it highly visible, it has not been hit at
all and it's been about 3.5 years.
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