How much effort is it to redesign for a custom tube size? Is this an exercise that others have done or is it easier said then done?
I think 1” EMT (29.54mm) would be more convenient (and maybe slightly more rigid). Or if I’m making a trip to the metal supplier then why not slightly bigger OD like 1.25” to 1.5”?
Thx!
That is a redesign of all parts including the flat ones. If it works pretty good as is, a full redesign is not worth it as it would be slight gains with a draw back of more expensive shipping and longer print and cut times. More importantly the surface finish and precision of conduit as you get larger goes down.
At some point I can look into what size conduit is available worldwide and see if there is a common size.
Thanks for the feedback! That amount of effort is what I was afraid. I’ll just stick to the current design. I was thinking I might need more rigidity because I’m considering a 5’ wide machine (and “if I’m going to go buy special tube then let’s get 1.25in”). But I suppose I can increase wall thickness too. I’ll run some numbers to see what wall thickness would be needed to keep the same amount of deflection as a 4’ wide machine… maybe it’s negligible.
So I ran some calculations to see what wall thickness I would need on a 5ft wide machine to keep the deflection the same as a 4ft machine (that uses the 1in OD tube and 0.065in wall thickness). As you may know, adding material on the inside is not very efficient, and it turns out I would need to double the wall thickness to 0.12in.
Calculation as follows:
It looks like the Dewalt router is about 4lbs and I’m guessing the rest of the center assembly is maybe 4lbs and then rounded up to a 10lb load, split over two tubes, so 5lbs each tube. I approximated the unsupported length by using the “usable width dimension” + 8in. So a 4ft table would have a tube length of 56in between supports. Using these inputs the 4ft table will have 0.030in of deflection at the center of the table. Seems like a lot of deflection, but if you’re cutting right through it probably won’t matter much and if you’re making a small piece it shouldn’t matter much. A 5ft table (68in unsupported tube) would have 0.054in of deflection, which is approaching 1/16" and seems more significant. If a 0.120 wall is used on a 5ft table then the deflection would be 0.035in.
I’m curious if the 10lb load is reasonable and if my approximation of the unsupported tube length is about right.
I’m also curious for those who have a 4ft table… if you run a pass along the x-axis, what is the depth at the sides compared to the depth at the center?
If we want it really rigid, like less than 0.010in of deflection, then a 1.5in OD, 0.065in thick tube would work nicely 
For reference, I made a tube deflection calculator which can be found here.
Keep in mind, the tables are also hard to make very flat. Z differences of 1/16" don’t usually make much difference. The exception is carving, where the width of the cut is determined by the depth. You’ll need a different strategy for that kind of cut anyway, like breaking into smaller pieces or surfacing the spoil board, or mesh levelling.