Medium Duty EMT?

What are your thoughts on Medium duty or heavy duty EMT? The medium duty EMT has an OD of 1.02" with an ID of 0.86", the Heavy Duty is OD 1.05" with ID 0.88". Of course the standard EMT from HD is OD 0.922 and ID 0.824. So wall thickness is:

Heavy duty: 0.085"
Medium Duty: 0.08"
Standard: 0.049"

Looks like the best deal is the medium duty. I can get a 10’ stick from Grainger for $35. What size MPCNC to download 25.4? 0.02" on the OD should be fine I think. This is a much better deal than steel tubing with a 0.062: wall thickness. Just not sure I can get straight sticks from Grainger?

According to the Engineering ToolBox, intermediate metal conduit (IMC) has an outside diameter of 1.029". If we compare this to 1" tubing, they differ by 0.74mm. Ryan created separate versions of the 3D printed parts for 1" (25.4mm) and 25mm, which are only 0.4mm apart. Based on this, 0.74mm is too much of a difference for Ryan’s parts unmodified.

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And modifying the parts, while not necessarily verboten, is certainly non-trivial, especially since you’ll be doing it from STLs, not from the CAD.

If you’re just musing, I’d say it’s not worth it. If you have a specific concern or use case need, let’s hear it, and someone can point you in the right direction to assuage your worries.

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Having reworked parts from the Primo and Burly from the STL files, I totally agree with you about a redesign being “non-trivial,” but there may be another approach. A couple years ago I read a topic on this forum where someone built a machine using 1" *conduit." While he had to do reauthoring of some of the 3D printed parts, and he made hardware changes, he primarily (according to the OP) just scaled most of the parts. I wonder if a similar approach could be used here.

The parts would need to be scaled up by 0.29% give or take…you might get away with a 2% scale.
Substituting 8mm bolts will take up some of the slop in the bolt holes and still work with the 608 bearings. There is a significant risk here since a person could go down this road and have a poorly or not functioning machine at the end.

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Which is why I suggested enumerating the rationale behind using Medium Duty EMT. Is it just musing, or is there a serious concern behind it? If there’s a real concern there, perhaps we, as a community, can address it before anyone wanders off into the weeds with the alligators and 'skeeters…


It was @blainesgarage but somehow he vanished from the face of the forum… :frowning: See here: 1” EMT conduit Primo XL project 1.163”/29.5mm