7 ms·

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'

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

elsewhen 2y ago
they have a video where they stress tested a table made out of EMT https://www.youtube.com/watch?v=1oCEMd4v9B4 https://www.youtube.com/watch?v=1oCEMd4v9B4
- hackcasual 2y ago
  Wild stuff. You can see the bottom horizontal trusses bending when loaded. EMT is just too thin walled for serious structural applications
Animats 2y ago
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 https://www.easyfit.com/catalog
- fidotron 2y ago
  What are the right keywords to use when searching for the fittings? My ali efforts often get flooded with nonsense.
  - DannyBee 2y ago
    Pipe racking connector Modular pipe connector Those do okay without you getting hundreds of irrelevant air hose fittings
  - bluGill 2y ago
    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.
    - potato3732842 2y ago
      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 2y ago
        I would nit-pick about your cantilever worktable failing because of a crappy fastener, killing your cat. Child even?
        potato3732842 2y ago
        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.
        quickthrowman 2y ago
        “Don’t buy fittings made from Chinese pot metal” is a simple way to avoid catastrophic failure due to substandard materials.
        night862 2y ago
        It just isn’t very absurd to worry that the question mark brand of load bearing fasteners are properly rated. I avoid the issue by not buying them, a lesson learned from my experience working in the QA field. I wouldn’t expect a teenager to have learned this lesson.
  - rpcope1 2y ago
    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 2y ago
      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.
  - deleted 2y ago
    [deleted]
jalk 2y ago
And that’s even with his feet on the ground out of frame ;)
dddw 2y ago
Good to know, my first thought seeing this way. I could build a raised bed. You save some lotta time
- DannyBee 2y ago
  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
DannyBee 2y ago
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 2y ago
  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 2y ago
    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 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 2y ago
      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!

elsewhen 2y ago

they have a video where they stress tested a table made out of EMT https://www.youtube.com/watch?v=1oCEMd4v9B4 https://www.youtube.com/watch?v=1oCEMd4v9B4

hackcasual 2y ago
Wild stuff. You can see the bottom horizontal trusses bending when loaded. EMT is just too thin walled for serious structural applications

Animats 2y ago

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 https://www.easyfit.com/catalog

fidotron 2y ago
What are the right keywords to use when searching for the fittings? My ali efforts often get flooded with nonsense.
- DannyBee 2y ago
  Pipe racking connector Modular pipe connector Those do okay without you getting hundreds of irrelevant air hose fittings
- bluGill 2y ago
  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.
  - potato3732842 2y ago
    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 2y ago
      I would nit-pick about your cantilever worktable failing because of a crappy fastener, killing your cat. Child even?
      - potato3732842 2y ago
        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.
        quickthrowman 2y ago
        “Don’t buy fittings made from Chinese pot metal” is a simple way to avoid catastrophic failure due to substandard materials.
        night862 2y ago
        It just isn’t very absurd to worry that the question mark brand of load bearing fasteners are properly rated. I avoid the issue by not buying them, a lesson learned from my experience working in the QA field. I wouldn’t expect a teenager to have learned this lesson.
- rpcope1 2y ago
  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 2y ago
    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.
- deleted 2y ago
  [deleted]

jalk 2y ago

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

dddw 2y ago

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

DannyBee 2y ago
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

DannyBee 2y ago

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 2y ago
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 2y ago
  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 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 2y ago
    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!