More than twice
I see most UK MPCNC builds using electrical conduit in 25mm from Screwfix (a hardware store chain with branches everywhere). I tried it but I got some binding and used stainless. However Galvinised conduit Its also available in 20mm and a quick search looks like its also available at other suppliers. Canāt find an option for 30mm.
We donāt really have a chain of local metal supermarkets here in the UK and I think many would be ordering mail order.
The place I use for a lot of my metal is RapidMetals.co.uk but there are others that do online and delivery. I had a quick look and you can get stainless and galvanised tube in various diameters. 30mm stainless but not galvanised tube only 33.7, 26.9 its also getting really expensive. The standard 25mm coinduit from Screwfix is just Ā£13 for 3m (16.5USD), but youāre looking at more like Ā£40 for 33.7 tube including delivery. I think that would be a bit of an barrier to many.
So depending on what you need it for by far the easiest option here in the UK is 25mm. If its diamater is really critical then maybe a specialist supplier is needed anyway and 30mm stainless would be the best option.
If anyone else has other options here in the UK for suppliers be glad to hear about them.
17/M 30mm 1.5mm wall stainless, Stainless Steel (304) Tube 30mm x 1.5mm Wall - Rapid Metals
Is it the same as around here, Metal supplies do not carry conduit? For that the local hardware store, or elctrical supply house.
6/m, much better.
You can get glavanised tube though sold as handrail hereā¦
and also more sizes hereā¦
Which does work out quite a lot cheaper than Ā£62.80 for 3m of the stainless.
Like you say, if you want it locally off the shelf then 25mm conduit is the best bet and very cheap.
Moving up a size is looking like more than 2.3x stiffer, worth poking around be the dims get set in stone.
Assuming its rigid tube and needs to have some rust protection, galvanised, limited sizes. 20 and 25 seem standard here and widely available but shopping around I can get 30mm, 32mm, 33.4mm, 33.7mm. Everywhere seems to sell tube in a slightly different diameter perhaps thatās just an error in converting to metric?
I think trying to find a off the shelf tube in ~30mm diameter is possible, but unless everyone uses the same supplier I think getting them all the same could be tricky. Could there be allowance for some range of tolerance? Iām thinking that imagine you place a mail order order for a 3m lenght of tube and it comes out .5mm different than quoted. I think Iād just pay more and get it from a metal supplier so I know its going to be right first time and not have to reorder. Also I suspect some of this stuff will have a seam.
Sorry not that helpful.
or
https://www.cef.co.uk/catalogue/categories/steel-conduit-hot-dipped-class-4-steel-conduit
That is the part I am trying to figure out. The conduit you are showing is considered ārigidā conduit in the US, we are looking for thin walled or interior (it will not be threaded as it uses slip fit connectors). If that is available in your area the Outside dimensions will be very consistent. If it is not available in your area, it will need to be purchased from a metal supplier as āTubingā at 30mmOD.
not a requirement. 30mm OD 1.5mm wall minimum, galvanized or stainless, seamless (or DOM) can be used if you wax it or something to help with rust.
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30x2mm also commonly available in Germany 
Edit: I just saw the Post from @Tokoloshe even with prices. That selection looks great
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Is this for a update of the Primo or LR3 or a completely new machine?
Iām about to update/rebuild parts of my Primo and would not be thrilled to do it just before a new design comes outā¦
I have added this here from another thread - in Aus, commonly available is 31.8 (31.75) Which is quite a lot larger than 30 and that seems strange to me, I assume because we get some imperial castoffs?
Probably the LR.
The lowrider, No plans to update the MPCNC for at least 6 monthsā¦but it is due. The LR is jumping in line because I had an idea.
So again we are at 3 sizes, I canāt catch a break.
29.5mm - US 1"conduit
30mm - international equivalent conduit, or tubing
31.75mm - āUSā Tubing 1 1/4"
I will see if I can make those all work.
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Every time you feel frustrated, imagine living in a fully metric country where tubing is sold in āUS sizesā - the metric equivalent is 31.75 while the rest of the world gets to use a completely illogical multiple of ten millimetres.
It must be so confusing for them! 
And then add in the fact that we use a mix of BSP and NPT, too, but with the BSP being āmetricisedā but still based on an imperial threadform etc. Love it.
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BSP/NPT makes my head hurt. About the k ly thing I need BSP for anymore though is the threads on my Japanese engineās oil pressure sensor.
While Canada is nominally metric, sharing our only land border with the USA means we have a de-facto imperial sustem, with a few hold-outs.
We will sort of accept units of measure in pints, quarts and gallons, but not US measures. I have had discussions involving fuel economy with some ā¦ less enlightened individuals, and of course state my results in L/100km, which is, I believe a world-wide standard. Other person not willing to convert needs miles per gallon, which my meage calculator will provide when fed litres of fuel for kilometers travelled, but I forgot that of course this guy was expecting it in a unit of measure standard in no other country in the world, so he couldnāt believe the resultā¦ Anywayā¦
We get many products that come in multiples of 946mL, sometimes 1147mL, though thatās becoming more rare as fewer places still use imperial quarts, and of course 1L.
For lumber, itās getting to be a mixed bag, complicated by the fact that nothing in lumber is actually its nominal size.
Steel and metals are also weird here. You will see 3/4", and 20mm side by side in the shops, and sometimes weird combinations, like 36" of 20mm bar, or even weirder, 25mm by 1/8" bar stock.
Just finished my MPCNC build last week. Both 25mm conduit and 1" DOM are available in the UK. Supply from Screwfix is correct but need to check carefully for bends. Importantly the 25mm conduit was too small for the gantry pieces and I needed to purchase a couple of pieces of the 1"DOM for the gantry. Your files for printing are remarkably accurate and I couldnt close the gap reliably around the 25mm conduit.
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