What size steel to use?

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How do you know what size steel to use on your projects that don’t have prints that an engineer has called out specifically for? Example; I want to build a welding cart, how do I figure out what size square or round tube to use, and what wall thickness to use? Or build an awning frame? What resources are there to figure out how much of a load a certain size steel can hold safely?
Reply:I would do the engineering But most just look at something like plan to build.  FYI Most shops use through and payer engineering.  About the only industry that does all time engineering is metal buildings. Dave

Originally Posted by BlinderGrinder92

How do you know what size steel to use on your projects that don’t have prints that an engineer has called out specifically for? Example; I want to build a welding cart, how do I figure out what size square or round tube to use, and what wall thickness to use? Or build an awning frame? What resources are there to figure out how much of a load a certain size steel can hold safely?
Reply:Lot's of ways to get around lacking the engineering knowledge.  (Plus a hint - even the engineers don't run calculations unless it is important...).Easiest is to look and ask.  Find a similar situation and see what they used.  If it works there, it will work for you in a similar set up.  This is more important with stuff like you said awnings where failure could be ugly.  A welding cart?  It matters very little what you use and is easy to go so overboard that you can't push the thing. You need shelf brackets? Grab a caliper and head to Home Depot and see what the available shelf brackets are made from and how they are done.Some of my personal guidelines:  General purpose stuff: 1/8" wall is great. Thick enough to be easy to weld but not so thick as to add excess weight.  Really thin stuff is much harder to weld than thick stuff, BTW.  When using square tubing for a frame, common sizes are anything from 1" sq to 2" sq.  A heavy welding table frame and legs you want heavy so 4" sq with 1/4" or slightly more wall is nice, but you can go smaller/lighter, especially on a small table. Again 1/8" wall is a nice, easy choice.  14 ga is a bit lighter but not so much that it is a horrible challenge to weld.Other things depend on the use.  A handrail has specific dimensions that it must meet for code.  Using those dimensions can make a lot of sense in other situations if you want to get a firm grab on something with your hands.  Also design can easily trump the material sizes.  A well-gusseted frame can be made much lighter than an un-gusseted one, or alternately be a lot stronger in the same thickness.  For example.But the best advice is to look at existing stuff and copy.  Hard to go wrong that way.  This really only becomes an issue in life and safety situations.  Don't make a trailer to drive on public roads or a metal building unless you know what you are doing or get an understanding of exactly what is required.Good luck and don't overthink it.-DaveXMT304 with: 22A Feeder, or HF251 Hi Freq DC TIG air cooled
Reply:I agree with a lot of what Dave said. Don't reinvent the wheel. If you can copy something that you know is kosher, by all means. FWIW, whenever I've built anything out of steel by gosh and by golly ("that looks about right") and then later did some crude calculations of how strong it was, it was generally between 100X and 1000X stronger than I needed it to be. I don't know that this information is of any help to you, but in my experience, unless you're working on heavy equipment or something structural that must not fail, like something for overhead lifting, the steel is usually far stronger than I would expect, and building it closer to the edge of the envelope (for example to save $ on material) would just make it LOOK too "flimsy" whether or not it was too light for the intended purpose. You can do an awful lot with gussets and triangular braces...google "monocoque construction."A36 mild steel has a yield strength of 36ksi tensile, meaning that to permanently deform (stretch) a bar 1" square would require a tension load of 36k pounds, or 18 tons. Shear strength is typically 75% of tensile strength. You can do a lot with just those numbers...for more important projects, there are tables and references out there such as at the "Engineering Toolbox" website. Some other good references are the books "Design of Welded Structures" by Omer Blodgett and "Metals and How to Weld Them," both available at used book sites (alibris.com) and the Lincoln Welding Foundation. Good luck and welcome to the forum.Last edited by Kelvin; 4 Weeks Ago at 05:53 PM.
Reply:That post above is really good.   The stuff I built early in my career was wayyyy overkill and then it wouldnt have been so bad if I didnt complicate it on top of that.Last edited by Sberry; 4 Weeks Ago at 06:24 PM.www.urkafarms.com
Reply:For a beginner a guy could look at a cart as some practice and it can be but a real diy guy is a salvage master. I find as much ready built as I can and even do some conversion/remodel with a lot of consideration to secondary finish.   Some of that HF stuff, even the engine stand might be a candidate but old grill frames make for free and a lot of pre bent pieces so hard toi do even if you had the tools, I cut that stuff up, toys, appliances, anything with free wheels.www.urkafarms.com
Reply:Here is a piece.  My neighbor was tossing an old range out, had this bottom, I added a piece of angle and about 10 sheet metal screws to stiff it up, screwed the wheels on and had a cutout counter top we stick on it and free, could paint it any color, that is the original but if you started with bare material it would have cost and needed to be finished.

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Last edited by Sberry; 4 Weeks Ago at 06:35 PM.www.urkafarms.com
Reply:This is a little cart from a grill that we whipped up toi store the fridge equipment.  Its stored out of sight so its not really well finished but fit the space it is intended for.  I rarely use it, dont want it in the way or for it to be damaged and fit it to a cubby behind another bench, gets a shirt tossed over for dust, no one ever sees it.  Sawed the wings off the one side and welded to the other to make custom handles.  The sheet made the shelf.  Thgat kind of stuff is even easy to scuff and paint.  The real upside is,,, it pays, it was cheap, free stuff, fast to do and couldnt have bought a bunch of stuff that worked as well.   I have done plenty of from scratch custom build but today its so much easier to be custom rebuilder in a lot of cases.

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Last edited by Sberry; 4 Weeks Ago at 06:49 PM.www.urkafarms.com
Reply:The one above is just strong enough.  It gets parked, if it is moved its on smooth floor. Didnt even consider the thickness but the shape and width of the frame was crucial to the design, strength not so much. One below started off as something else and is on its 3rd generation or so. They were carts for carrying bolts of fabric in a factory and I got a bunch at an auction.  They were heavy duty, pipe and some rebar bracing, good wheels.  I made all kinds of stuff, have 4 left with wheela and one the frame as steel rack. This one has 1/4 plate top. Own light and 20A circuit.  Same cart, different stuff.  The cost to build would be,,, well.  Hard to do this without a welder.

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Last edited by Sberry; 4 Weeks Ago at 07:10 PM.www.urkafarms.com
Reply:That does not look like welding equipment. I do not see a tube test?Dave

Originally Posted by Sberry

The one above is just strong enough.  It gets parked, if it is moved its on smooth floor. Didnt even consider the thickness but the shape and width of the frame was crucial to the design, strength not so much. One below started off as something else and is on its 3rd generation or so. They were carts for carrying bolts of fabric in a factory and I got a bunch at an auction.  They were heavy duty, pipe and some rebar bracing, good wheels.  I made all kinds of stuff, have 4 left with wheela and one the frame as steel rack. This one has 1/4 plate top. Own light and 20A circuit.  Same cart, different stuff.  The cost to build would be,,, well.  Hard to do this without a welder.
Reply:Another thing a lot of beginners do (or at least I did) is overweld stuff, I guess because we like welding and want to practice. "If a little is good, more should be better, right?" Usually not with welding. Overwelding things can cause all kinds of problems with warping and distortion, and cutting everything apart to straighten it our is just that much more work if every freaking thing is welded all together. With my first "major" project (a welding table), I remember I overwelded the legs, and they got warped all out of plumb, and it seemed like I was there forever with a torch cutting through fillets on top of fillets trying to cut it apart enough to sledgehammer the legs back plumb...
Reply:Welding cart is fine if made with either 14ga, or 11ga square tubing.  11ga is easier to weld.For anything that has to carry some real weight, it's best to find something that will calculate stress, deflection, and moments.  BeamBoy V2.2 is a very good elementary software program for analyzing stresses.  It's open source software.
Reply:

Originally Posted by farmersammm

For anything that has to carry some real weight, it's best to find something that will calculate stress, deflection, and moments.  BeamBoy V2.2 is a very good elementary software program for analyzing stresses.  It's open source software.
Reply:Everything doesnt have to be made out of tubing either.www.urkafarms.com
Reply:For welding carts, look at youtube. They will give you a good start for material types and sizes. .Last edited by milomilo; 4 Weeks Ago at 01:45 PM.ChrisAuction Addict
Reply:if thinner than 1/8" if you tapped holes its not thick enough to hold up.youtube got videos of people stick welding 1/16" and .040" thick metal with 6013, obviously it requires some expertise and I not sure howstrong the welds are basically using 3/32 6013 at 75 amps they are basically making a series of tack welds. or 5/64 at 55 amps for.040 thick metal. videos also showing filling gaps in thin metal too, some call it texas tig.youtube videos show SS tubing or railing done too that way, really guy not sure if using a helmet and wearing open toe sandals butreally they some do amazing cuts with hand held grinderLast edited by WNY_TomB; 4 Weeks Ago at 02:18 PM.
Reply:Always copy a known design when you can!  - GREAT advice given earlier that I can't agree more with.Larger is always stronger than thicker, going up in tube size will yield much more strength than going up in thickness.Generally,I like around 1" or larger tube for cart, dolly, laundry shelf type stuff, 16g (.0625") or thicker.     I've gone as low as .75" but that is for relatively short spans/light loads - about 3 feet or less, and mainly for aesthetics (and cost, these days).   Most hand trucks/dollies are made from 1" 16g (.0625") tube.I like 2" or greater for heavier stuff,  1/8"  .125" or thicker.     2" is extremely versatile, and common (usually cheaper)   2" is used for towing receiversTruss type shapes for spansLast edited by SlowBlues; 4 Weeks Ago at 12:59 AM.
Reply:I made mine out of all 16 ga: sheet, 1.5" sq tube, and 3/4" sq tube.  Plus a little 1/8" angle maybe.  I don't like the idea of overbuilding.  It doesn't appeal to my finer sensibilities....or my wallet.
Reply:It seems crazy to me that this much thought is put in to making a stupid welding cart. Where did common sense go?Miller 211Hypertherm PM 451961 Lincoln Idealarc 250HTP 221  True Wisdom only comes from Pain.
Reply:Best to look at other designs and copy their recipe.  Or if its for a customer tell them to spec it out...We've done so much, for so long, with so little. Were now qualified to do anything with nothing !
Reply:The reason i commemtbis i like to see the guys start economical instead of runni g to the steel warehouse for every piece.   One of the pieces next to the welder shold be a shelf for stock he collects.  Fabricating from trips to the steel warehouse get spendy fast.  Another piece to coat tail the welder should be battery sawzall and fistful of metal blades he scores on sale.  Battery drill and bits, nut drivers, dykes for wire.  Its often easy to glean pocket full of metal screws to throw in a tackle box.www.urkafarms.com
Reply:I dont usually watch vids but i do a few of that and he compares it to a 300$ cart would have been a bargain after dropping 130 pluss other stuff onone he build,,, i would have bought first unless i had a free tool box.www.urkafarms.com
Reply:This is cheap cart.

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Reply:When mentioning that and "engineer" was involved remember that an "engineer" is utilized to figure out the minimum standard, either cost wise or strength wise (equals cost in the end) to construct something.  Look at a mass produced article and realize that it is produced with cost to produce vs return on the investment motive.  If you want a welding cart idea look at an already designed cart.  If it is from a mass produced source it will be from formed material.  Use their design and build it out of at least 1/8" stock and you will already be ahead of them.
Reply:I use whatever they have at the steel yard that is not obviously overkill. Everything from 1x1x1/8 angle for a cart for my syncrowave (which weighed about 400 lbs) to 2x2x1/8th square wall tube for one of my welding tables. I have built some furniture tables from 1x1x14 gauge tube too. But I have never felt the need to go heavier. I think design (number and placement of cross members, gussets, etc.) is probably just as important as wall thickness on the stuff I have built. But I agree with the above, don't over think it especially for a welding cart.Miller Multimatic 255I was planning on retirement in 2018 in 2021 so purchased 1,000 pounds of steel Mostly angle iron 3/4" to 1 1/2" in 1/8" Some round 1/4" to 1/2" and little bit flat bar. When had shop it was limit size for what I need and was odd sizes like 3/4 x 6 to 1 x 12 flat bar not need in retirement Dave

Originally Posted by BlinderGrinder92

How do you know what size steel to use on your projects that don’t have prints that an engineer has called out specifically for? Example; I want to build a welding cart, how do I figure out what size square or round tube to use, and what wall thickness to use? Or build an awning frame? What resources are there to figure out how much of a load a certain size steel can hold safely?