[hackcasual]

EMT conduit isn't a great support material if you're handling human weight loads. The picture on the front page showing off the strength is visibly bending. It's kind of an awkward load profile, lower weight like an awning you're probably using ABS, higher weight you're using 1 1/4" system like steeltek or keeklamp

[Animats]

Right. There are many structural pipe fitting systems. Here's one.[1] Grainger, McMaster-Carr, and larger hardware stores stock them. Usually, they use bigger pipe. Fittings are really cheap on Alibaba.

[1] https://www.easyfit.com/catalog

[fidotron]

What are the right keywords to use when searching for the fittings?

My ali efforts often get flooded with nonsense.

[bluGill]

If it is structural I'd buy from a big place not Ali. Unless you have the ability to verify the material really has the claimed properties you need you should stick with a major trusted supplier who will either verify the factory produces fittings to spec, or test everything for you.

[fidotron]

If it is to support a human I would tend to agree, but for desks etc. I have found local supplies (Canada) have declined in quality to such a degree they need the level of QA on arrival the Chinese ones do while costing 5-10x as much.

[bluGill]

unfortunately the big box stores do not check quality. mcmaster which was pointed out above does and is a similar price. I am not sure about granger.

[potato3732842]

Paying big bucks for a paper trail is almost never cost or time effective compared to just adding safety factor for "normal applications".

And by "normal applications" I mean "please nobody be intentionally obtuse and start nit picking about aerospace applications and connecting rod bolts and whatnot".

[night862]

I would nit-pick about your cantilever worktable failing because of a crappy fastener, killing your cat. Child even?

[potato3732842]

There will always be a weakest link. At some point you just gotta be an adult and not build things to within an inch of their lives for the use they will see and then have the self control to not push the limit. Resources are limited and engineering tradeoffs are everywhere. These discussions always devolve into absurdity very quickly.

[bluGill]

I don't need the paper trail just the quality it provide. That is often available for much less.

[rpcope1]

If you're buying hardware that has any possibility of harming someone or doing any amount of non-trivial damage if it fails from AliExpress or Amazon, you're doing it wrong and should reconsider whatever it is you're doing. Even the hardware from HD is generally pretty shitty these days. If you can't afford or won't go buy it from Fastenal or MMC or somewhere reputable, where you can expect the hardware you're buying actually adheres to a stated grade or spec, you just shouldn't do it.

[fidotron]

I don’t know what you lot think is so dangerous about a few supports for netting that keeps the squirrels off the vegetables. Please spare us the safety lectures, we are adults.

[DannyBee]

Pipe racking connector

Modular pipe connector

Those do okay without you getting hundreds of irrelevant air hose fittings

[DannyBee]

Agreed. EMT exists to keep wire from getting damaged by accident. It isn't even considered self supporting let alone structural.

You can easily bend 1/2 emt by hand.

[quesera]

But 3/4" is also readily available, and much stronger. And of course larger gauges are available as well, just more difficult to bend with a standard manual bender.

I wouldn't use it for scaffolding(!) or anything supporting dynamic loads in the human-scale, but I've sistered three 3/4" EMT pipes together for an extremely strong, rigid, and inexpensive support pole.

[DannyBee]

Sure, you can use it for stuff, just don't expect it to hold anything real in any meaningful span.

Here's some real values for you:

2ft 3/4 EMT has an expected failure force of about 3300lbs (some studies found actual is around 3900-4200lbs).

4ft 3/4 EMT ha an expected failure force of about 2000lbs.

8ft 3/4 EMT has an expected failure force of about 450lbs.

So it is non-linear.

This is the point at which it fails catastrophically, not the point at which it starts sagging.

They are also not permanent load ratings, include no safety factors, etc.

Cost wise, 3/4 EMT costs 11 bucks for a 10ft piece at my home depot.

I can go to my local metal supply and get 3/4 square structural steel tube for < $1.00 a ft.

This is relatively in line with online suppliers so i believe it's not an exception: https://www.onlinemetals.com/en/buy/square-tube

This is structurally rated steel tube - it will hold much more than the EMT, it is meant for holding things, and being square, it's often easier to work with.

So i just don't know why i'd use the EMT.

[quesera]

EMT is light weight, readily available on weekend evenings, inexpensive, cuts easily, bends easily, is reasonably rustproof, and good enough for many applications.

It is "appropriate technology" for some applications, but of course there are better options when the requirements approach its critical limits!

I've used EMT to build big hoop trellises for growing vines. Bends smoothly into pairs of 10' arcs (using some ad hoc jigs), weighs almost nothing, requires minimal paint protection, supports more curcubits than our friends and family can consume, and lasts ~forever.

One of the tricks with EMT construction is to leverage the design for structural rigidity. E.g. geodesic domes with short members are extremely strong. Anything in compression will do well. If you need resistance to deflection across a long unsupported span, then I definitely agree -- EMT is not your material of choice!

[DannyBee]

(steel tubing is available on weekends and evenings too, fwiw)

I agree it's good enough for random aesthetic stuff, but even outdoor stuff is silly to use it for if you care about aesthetics. It really does rust pretty quickly these days. I have plenty of EMT that is 20 years old and not rusted, and plenty next to it that is 5 years old and rusty.

The latter is from different vendors, too. The specs over the years have gotten worse because nobody really uses EMT outdoors without painting it unless they are willing to accept it rusting to crap.

For your case, you could just use pvc pipe, cheaper, bends easier, cuts easier, can be glued directly, will never rust, you don't care about weight limits.

However, if you remember where we started, this article is about "structural pipe fittings" for EMT.

That is a horrible horrible idea.

[quesera]

PVC pipe does not survive outdoors, and the failure mode is messy.

"Structural" does not necessarily mean "very strong".

I think we mostly agree here though. I've used EMT for lots of things, and it has never ever let me down even slightly. I have also chosen square steel tubing for (less frequent) cases.

Choosing carefully is the key. When EMT fits, it's great stuff and preferable in many ways.

[hannasm]

Do you have a good source for these load calculations. I poked around on the site but didn't see anything representing an L/360 or other strength rating despite these fasteners being large enough to hurt people doing things if they don't know any better.

It would be great to just have one nice calculator to lookup trustworthy load data on standard home depot materials.

[jalk]

And that’s even with his feet on the ground out of frame ;)

[elsewhen]

they have a video where they stress tested a table made out of EMT

https://www.youtube.com/watch?v=1oCEMd4v9B4

[hackcasual]

Wild stuff. You can see the bottom horizontal trusses bending when loaded. EMT is just too thin walled for serious structural applications

[dddw]

Good to know, my first thought seeing this way. I could build a raised bed. You save some lotta time

[DannyBee]

Emt will eventually rust if not painted as well, depending how much you care. It is really mostly used in open commercial/industrial settings (if you go to home depot or Costco you will see emt running everywhere). Aluminum is your obvious metal winner for this sort of thing outdoors (cost wise). PVC, even thick wall, becomes brittle pretty quickly in sunlight.

This is why you see wood or outdoor plastics for raised garden beds