Stainless Steel - Quick and dirty flex test

I bought some 1" OD stainless Steel this week, and the flex difference is pretty obvious. I didn’t setup the dial indicator but took some quick pictures.

I had 6’ lengths of tubing supported on both ends and hung a 10lb weight form the center point. I took a picture from as level as I could get to illustrate the flex.
The standard EMT that we/I have been using was a bit more rigid than the .0185" stainless curtain rod (too weak the bearings left a groove on the first pass).

The 316l stainless did better what I tested what was sold as .049" and .083" wall thickness. The .049" is much better than the EMT but really close to the .080" and about $10 cheaper per 6’.

I would recommend .050" if you want to upgrade your machine and have some money to spend.

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Where do you find stuff like that?

I found some at a hardware store (shower curtain rod), amazon, and a local supplier.

I’m strongly considering ordering some of this unless I just go with regular emt.

I’d like to point out that, for some reason, 0.065" wall thickness 304 stainless steel tubes are about half the price of 0.050" ones, at least at speedymetals.com (http://www.speedymetals.com/c-8276-round-tube.aspx?thickness=1). They seem to be the lowest price I could find - a quarter per inch or like $10 for 4’. 0.050" on the other hand is $0.48 per inch, $19 for 4’.
I ordered custom cuts from them as I’m building an odd size 27" x 40" (to match a space under my desk where my MPCNC would have to be stored between uses). A bit more expensive than buying whole-feet size but beats having to invest in a tube-cutting tool and cut yourself.
Shipping was $20 though.

1" or 1.05" OD SS Tubing Is 3/4 ID If i’m not mistaken… a quick search on amazon also confirmed that and really 1" OD was 3/4 ID… but this 316L stuff is $100 for a 3 footer… that’s crazy expensive… any chance anyone’s used 304? I cannot get 316L locally and people want crazy money for it.

Uhh, if it’s 1" OD and 3/4" ID, then it’s 1/4" thick wall! It’s crazy expensive because it’s crazy thick!

wuddn’t that be 1/8" wall thickness barry?

1/8"+1/8" =1/4"
1"- 1/4" = 3/4"

ur forgetting that its tubing so you would split the difference in half to find the wall thickness

I just ordered some 304. When it gets here, ill do the a test and provide some pictures. I don’t have any 316l to compare it to, but maybe this info will help.

Thanks,
John

@Walt, yea, you’re right! I ain’t got no good math, or english! :wink:

What are you thoughts on tweaking the files and running 3/4 Gas Pipe or Rigid Conduit, both are 1.050" Diameter. Should be a lot stronger than EMT and still reasonably priced (about $10/10 ft stick at any Menards/home depot). Or does the extra weight start to become an issue?

Yea, now you’re throwing around a lot of extra weight.

Plus all that extra weight actually makes the pipe more prone to sagging not less. what you want is added stability not added weight. while stainless is slightly more heavy than zinc plated, dots extremely more rigid along its span. there’s always going to be a trade off.

my local source 1.5mm wall 304 stainless is really cheap. around 30 bucks for 6 meters.

On my machine, I use tubing initially designed for guide rails in the industry. Very heavy but it is impossible to bend. You might want to consider this option for a CNC if you have big loads.

Heavy=no good

Did 304 SS work out?
Thank you in advance.
Kn

Well, it doesn’t bend at all.
I could compare with standard tubing using weights and a comparator if you want, I think I still have about 30 cm left of both type of tubes, But I’m pretty sure the big ones will win the comparison easily. You can feel the difference just trying to bend them by hand, the heavy ones don’t flex at all. They are made of hardened steel, I guess the difference comes mainly from there.

IMG_348dd4.jpg

I presume that it has been asked and suggested many times over:

What about square tubing?

The theory:

I’ve been using this calculator:
https://www.easycalculation.com/engineering/mechanical/mechanical.php

Round tubes:

  • steel tube
  • 1" diameter - I will use international version 25mm
  • 0,08" (2mm) wall thickness
  • 40" (1m) long
  • 20 pounds (10kg) weight (it’s just a presumption that 84oz/in steppers could assert such a force on a beam)

Deflection - 0.577"

Square tubes:

  • steel tube
  • 1" x 1" - I will use international version 25mm x 25mm
  • 0,08" (2mm) wall thickness
  • 40" (1m) long
  • 20 pounds (10kg) weight (it’s just a presumption that 84oz/in steppers could assert such a force on a beam)

Deflection - 0.010"

Everything’s the same except the shape
So, either the calculator is wrong (I’ve never used one so I couldn’t tell) or square tubes is far, far better solution.

Or I’m missing something?

I’ve checked local prices, square tubes are 20% more expensive.

Since no one remixed this design for use of square tubes I’m really getting something wrong?

Thanks!
Regards,
Walter

Hi Walter,

Thanks a lot for this very interesting tool.

If it is indeed accurate, it seems that wall thickness does actually matter quite a bit, which is in contradiction with what most people seemed to believe here.

One thing seems strange to me: titanium appears to have more deflexion than steel. Isn’t titanium supposed to have better strenght characteristics than steel? (or maybe it is just far lighter for relatively similar characteristics?)

Anyway, thanks again for this link